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Science 9 Chapter 19 – Simple Machines 19.1 Forces • A force is a push or a pull Force effects – A force may: 1. Cause a change in an objects shape 2. Set a stationary object in motion 3. Speed up a moving object 4. Slow down a moving object 5. Stop a moving object 6. Change the direction of a moving object - Any object in motion will continue in motion unless a force acts in the opposite direction o Any motion that results depends on the size of the force and the mass of the object Unbalanced forces: One object is exerting a greater force than the other object. This results in one object moving o Push on a book – the force from your body is greater than the force of friction so the book will move in the direction of the greater force (the direction you are pushing) o Tug of war Balanced forces: Two objects are exerting equal forces on each other. The objects don’t move. o Push against a wall, the force from your body equals the force in the opposite direction, the wall doesn’t move Types of forces: 1. Friction – Always resists motion when one material rubs against another caused by rough surfaces getting caught on each other Puck on smooth surface Puck on rough surface (little friction) (little friction) 2. Gravity – Another force which results between any two objects attracting each other • Gravity can speed things up going downhill, or slow things down going uphill • You are attracted to the earth because of gravity • The force of attraction between things is measure in Newtons (N), named after Sir Isaac Newton • One Newton (N) force is the equivalent of an orange pushing down on your hand Mass and Weight • Mass is the amount of matter an object contains usually measured in kg or g • Weight is the amount of force that gravity exerts to attract an object. Gravity exerts a force of about 10N on each kg of mass • If you know the mass of an object, you can find the force of gravity. F = m x g (g = speed of gravity = 10 m/s2) Ex. For a 3 kg object, F = (3 kg)(10 m/s2) F = 30 kg m/s2 = 30 N The force of gravity is 10N per kg on earth, The force of gravity is 1.7N per kg on the moon, The force of gravity is 25N per kg on Jupiter. For a 54kg person, fill in the table below: Earth Moon Jupiter Mass 54kg 54kg 54kg Weight 540N 90N 1350N Do Review questions 19.1 Pg. 414 19.2 Force and Work Force is measured using a spring scale (units are Newtons) Work – Transfer of energy to an object • Depends on the size of the force used and the distance the object moves W = F x d W (Joules) = (Newtons) x (metres) F d • One Joule is the amount of work done when a force of one Newton moves an object one metre ( 1J = 1 Nm) Ex. A person uses a force of 200 N to push a box 1.5m. How much work was done? 1. Write down the data you know, and the info you need to find out F = 200 N d = 1.5 m W=? 2. Write down the equation W=Fxd 3. Substitute and solve with units W = (200N)(1.5m) = 300 N m = 300 J 4. Make a final statement answering the question The work done was 300J Science 9 – Forces and Machines Name:______________________ Date:___________ Block:______ 1. Give the full name of the standard unit for force, as well as its symbol 2. Use a diagram with arrows to describe the following forces. (Use the same diagram for a-d, and the same scale for all of your four force arrows) a) 5N acting upwards b) 10N acting downwards c) 8N acting to the left d) 3N acting to the right 3. How much force is needed to lift a) a 1kg bag of apples b) a single 100g apple c) a 10kg box of apples 4. Which would probably require the greater force, lifting a 50kg sack of potatoes or dragging it along the floor? Why? 5. Which of the following are measure of force, and which are measures of mass? a) 60N b) 45kg c) 32t d) 800N 6. Calculate how many joules of work are done in each case a) F = 5N, d = 0.5m b) F= 16N, d = 30m c) F = 0.5N, d = 0.1m 7. A physiotherapist exerts 18N of force to move a patient’s arm a distance of 0.6m. Calculate the work done on the arm. 8. A bulldozer exerts a force of 6000 N to move a rock a distance of 45 m. How much work was done on the rock? 9. A teenager’s hand moves an average distance of 7cm when lifting the pull tab on a can of juice. The average force exerted on the tab is 8 N. How much work must the teenager do to open ten cans of juice? 10. A plasterer’s helper exerts a force of 500 N to hold a sheet of drywall still while someone else nails it in place. How much work did the helper do on the drywall? 11. A reporter picks up a microphone having a mass of 100g. a) How much force is required? b) How much work is done when the microphone is lifted a distance of 0.10m? 19.3 Doing Work with Machines • Simple machines are an extension of the topic energy which was begun in Sc 8 with heat, light and sound and will be followed in Sc 10 with electricity and magnetism o A simple machine is anything that makes it easier or more convenient to do work. o 3 ways a simple machine can do this is by: 1. letting you exert less force (Multiplying a force) ex. a car jack allows you to lift a car with less force 2. letting you do work faster (Multiplying speed) ex. Bicycle pedals require less distance to be pushed than the distance the tire turns in one revolution 3. letting you exert the force in an easier direction (Changing direction of a force) ex. A flag can be lifted up a flagpole by pulling down. o Machines do at least one of the following jobs: 1. Transfer forces from one place to another • Hand generator transfers from hand to motor 2. Transform energy from one form to another • Hand generator transforms mechanical E to light E 3. Change the direction of a force • Pulley changes downwards pull to an upwards pull 4. Multiply speed or distance • Bike pedals multiply the speed of the tire 5. Multiply force • Little force on lever lifts a large weight Mechanical advantage is the amount a machine can multiply a force Mechanical advantage (MA) = Load force (FL) / effort force (FE) o Where load force is the force without the machine (the force the object has, usually FL = m x g) o Effort force is the force with the machine (the amount of force the machine exerts, usually given) Ex. Lifting a box requires 110N, but if you use a pulley, you only use 10N. What is the mechanical advantage? 1. Write what you know and what you need to find out Load force = 110 N Effort force = 10 N Mechanical advantage = ? 2. Write the equation Mech adv = Load force / effort force 3. Substitute into the equation Mech adv = 110N / 10N = 11 4. Make a final statement The mechanical advantage is 11 Science 9 – Forces & Machines Name:______________________ Date:___________ Block:_______ 1. What is a machine? 2. Lifting a friend in a wheelchair straight up onto a porch requires a force of 900N. With a ramp, the effort force needed is only 150N. Calculate the mechanical advantage of the ramp. 3. To have repairs made on its underside, a 40 000N railway car is pulled up a ramp and onto a raised platform. The effort force needed is only 5000N. Calculate the mechanical advantage of the ramp. 4. A 3200N boat is towed up a boat ramp. The truck pulling the boat exerts an effort force of 500N. Calculate the mechanical advantage of the boat ramp. 5. A nurse uses a force of 200N to push a wheelchair up a ramp to the door of the hospital. The wheelchair and patient weigh 800N. What is the mechanical advantage of the ramp? 6. A cook does 1000J of work on a hand-operated food grinder. The grinder does 750J of work on the food. Calculate the efficiency of the food grinder. 7. A pulley system is used to lift a 1200N engine a height of 0.9m. The mechanic exerts an effort force of 200N and pulls the rope a total distance of 6m. Calculate the efficiency of the pulley 19.4 - The Six Simple Machines: 1. The inclined plane • A sloping surface like a ramp • The more gentle the slope, the greater the mechanical advantage • A hiking trail is a ramp 2. The wedge • A wedge is like a ramp, put is pushed into or under an object o Can be used to split objects or prevent an object from moving • The longer and narrower the wedge, the greater the M.A. • Examples are needles, knives, axes 3. The screw • A screw is an inclined plane wrapped around a rod • Able to enter hard objects like wood easily • Corkscrews, jar lids are also screws 4. The lever • The lever is a bar supported at one point called the fulcrum and rotates about this point • There are 3 different ways levers can be arranged E E E L L L First class lever Second class lever Third class lever Ex. hammer (pulling Ex. Bottle opener/ Ex. Fishing Rod/ out a nail), prybar wheelbarrow human arm Multiplies Force Multiplies Force Multiplies distance and speed Mechanical Advantage/Levers Example: Mechanical adv = load / effort = 3600N / 600N Load of =6 Effort of 3600N 600N The location of the fulcrum in this 1st class lever will determine how much mass you can lift. The closer the fulcrum to the load, the less effort you will have to apply (or the more mass you could lift) Ex. FL = 3600 N FE = 600 N In order to raise the bus 0.1m, the person must push the lever down 0.6m. FL = FE = dL = dE = WL = WE = * Thus, the amount of work done by the lever is no greater tha the amount of work done on the lever. Work is not saved by using a simple machine, actually extra work is often needed to overcome friction between the machine’s moving parts. 5. The wheel and axle • A large diameter wheel is attached to a small diameter axle or shaft • Screwdriver, pencil sharpener and a hand drill are examples 6. The pulley • A pulley is a rope looped around a support or wheel E E L L Single fixed pulley Single moveable pulley • These pulleys change direction of applied force • More complicated pulley systems multiply force and change direction of the force o In a fixed pulley, the load and effort forces are the same. o In a moveable pulley, all strings in the pulley share the load with the exception of the string that is pulled o If the string is pulled upwards, it is also included in sharing the load. o If the string is pulled downwards, it does not share the load, its only function is to change direction of the force (to make it easier to pull). Ex. If there are two strings, a load force of 100N will require an effort force of 50 N on each string. The mechanical advantage is 2. WE = FE x dE WL = FL x dL = 50N x 2m = 100N x 1m Both are equal to 100 Joules 100N (Remember that the movable pulley multiplies force, but does not reduce the work needed to raise the load. In order to lift the load 1m, the effort force must pull the rope through 2m.) 19.5 - Efficiency of Machines • The efficiency of a machine is a calculation of the work done by a machine (work output) as a percentage of the work needed to operate it (work input) The work done by a machine when it moves a load is called its work output (To determine this you must know the load Force and the load Distance (because W = F x d) The work done on a machine is called its work input (To determine this you must know the effort Force and the effort Distance (because W = F x d) Efficiency = Output / Input x 100% Ex. The energy in a fuel is 400kJ. When the fuel is burned in a motor, it produces 100kJ of energy. What is its efficiency? Efficiency = output / input x 100% = 100kJ/400kJ x 100% = 25% The energy is lost as heat and friction. Internal combustion engine cars are not very efficient. Sc 9 PROBLEMS INVOLVING WORK Name_________________ Date__________ Period___ Problems involving work are of three types. (1) You may be given the force and distance and be asked to find work. (2) You may be given the work and distance and be asked to find the force. (3) You may be given the force and work and be asked to find the distance. TYPE 1: FINDING WORK, GIVEN FORCE AND DISTANCE. PROBLEM: An object has a force of 5.0 N applied to it and moves a distance of 4.0 m. Find the work done. SOLUTION: The formula for work is Work = force X distance Thus, W = 5.0 N x 4.0 m = 20 N•m = 20 J TYPE 2: FINDING FORCE, GIVEN GIVEN WORK AND DISTANCE PROBLEM: 20 J of work are done by a constant force when it moves an object 4.0 m. Find the constant force on the object. SOLUTION: W = F x d or d = W = 20.0 N•m = 5.0 N F 4.0 m TYPE 3: FINDING DISTANCE, GIVEN WORK AND FORCE PROBLEM: 20 J of work are done on an object when a constant force of 5.0 N is applied. Find the distance the object moves. SOLUTION: W = F x d or d = W = 20.0 N•m = 4.0 m F 5.0 N Now try doing the following questions: 1. Calculate the work done in each of the following examples. (a) Force = 4 N, distance = 2 m (c) Force = 20 kN, distance = 3.0 m (b) Force = 120 N, distance = 3.60 m (d) Force = 8.0 N, distance = 150 cm 2. Calculate the force exerted in each of the following examples. (a) Distance = 20 m, work done = 500 J (c) Distance = 3.5 m, work done = 105 J (b) Distance = 480 cm, work done = 288 J (d) Distance = 4 km, work done = 20 kJ 3. Calculate the distance through which the force is exerted in the following examples. (a) Force = 40 N, work done = 80 J (c) Force = 400 N, work done = 30 kJ (b) Force = 2.2 N, work done = 660 J (d) Force = 2.5 kN, work done = 7.5 kJ 4. A force of 15 N is applied to a toy car and moves it 4.0 m. How much work is done? 5. A car travels along a level road a distance of 1.5 km. The forward force exerted by the road on the car is 200 N. Calculate the work done on the car in Joules. 6. A force of 350 N is required to push a piano having a mass of 400 kg. How much work is done to push the piano 5.0 m across the floor. 7. A car accelerates from 0 to 100 km/h in 8 seconds. It covers a distance of 100 m in this time. the engine does 300 kJ of work to accelerate the car. What is the average force exerted by the engine? Sc 9 FORCE, WORK AND MACHINES PROBLEMS Name_________________ 1. A hiker places a 12 kg backpack on the ground in order to open the door of a cabin. (a) How much force is required to pick up the backpack again? (b) How much work must be done on the backpack to raise it from the ground to the floor of the cabin, a distance of 0.3 m? 2. Four movers have to raise identical crates onto the back of a truck 1.2 m high. The first mover lifts the 850 N crate straight up and onto the truck. The second mover uses a 4 m ramp and exerts a force of 285 N. The third mover uses a very long ramp of 10 m and exerts a force of 140 N. The fourth mover tries to lift the crate but fails. (a) Which mover exerts the largest force? (b) Which mover does the most work? (c) Which mover does the least work? 3. A crane lifts a 500 kg box 10 m in the air. How much work is done? 4. An engine does 25 000 J of work lifting a 2000 N box. How far is the box lifted? 5. Four students run up a set of stairs 4 m high. The table below shows their weights and times. STUDENT WEIGHT TIME A 450 N 3.6 s B 800 N 6.4 s C 600 N 5.0 s D 500 N 4.0 s (a) Which student exerts the largest force? (b) Which student does the least work? 6. An inclined plane is used to push a 500 N load to the bed of a truck, a height of 2.0 m. The sloping surface is 10.0 m long, and the mover pushes with an effort force of 100 N. (a) Calculate the work output (work done by machine on load). (b) Calculate the work input (work done on machine by mover). (c) Calculate the efficiency of the machine. 7. A screw-type pump is used to raise 200 kg of water a distance of 3.0 m. The handle of the pump is turned with an effort force of 40 N a total of 1200 times tracing a circle of 20 cm circumference each time. (a) Calculate the work output. (b) Calculate the work input. (c) Calculate the efficiency. 8. A farmer uses a wheel-and-axle to raise a 1000 N feed sack to the loft of a barn, a height of 8.0 m. The handle of the wheel-and-axle must be turned 150 times to do this using an effort force of 100 N each time. On each turn, the handle traces out a circle 60 cm in circumference. Calculate the machine’s efficiency. MORE FORCE AND WORK PROBLEMS! (Be sure to show your work.) 1. How many newtons of force will it take to lift an object with a mass of 250 grams? 2. A force of 50 N is needed to lift an object. What would the mass of this object be? 3. What force would be needed to slide a 2000 g book across a smooth table? 4. A boy pushes against a 4000 kg wall with a force of 500 N. How much work was done? 5. A garage door opener exerts a 200 N force to move a door 2 metres. How much work has been done? 6. A 100 g object is lifted 5 metres. How much work has been done? 7. 800 N (a) Work output = ? 70 kg (b) Work input = ? (c) Load distance = ? 20 cm (d) Mechanical Advantage = ? (e) Can the job be done? Sc 9 Efficiency WS Name: ____________________ Date:_______ Period ____ 1. A cellular phone charger uses 4.83 J of energy per second. 1.31 J of this end up stored in the battery as chemical energy. a) What is the efficiency of the charger? b) What % of the energy is “lost” to other forms? c) What other forms could the “wasted” energy be converted to? 2. A solar panel receives 500 J of energy from the sun. 280 J of this ends up as heat, 105 J transmit through the panel as light, 40 J of light energy are reflected off the panel, and 75 J are captured and converted to electricity. a) What is the efficiency of the solar panel? b) What % of the energy is lost to heat? c) How many J of energy are lost in total? d) What is the total % of lost energy? 3. A windmill is hit by air with 20,000 J of energy per second. The function of the windmill is to convert the energy to electricity, and 5,000 J/sec are transferred to this form. What is the efficiency of the windmill? 4. Coal is burned to make electricity in a power plant. A coal-burning power plant is 33% effective. If a piece of coal containing 2500 J of stored chemical energy is burned, how much useful electricity can be harnessed? 5. A hydroelectric power plant converts the energy of falling water into electricity. The conversion is 90% effective. If 500,000 J of electrical energy are produced, how much gravitational energy did the water initially have? 6. Different kinds of light bulbs have different efficiencies. 150 J of energy are supplied to each of 2 light bulbs. The incandescent (regular) light bulb puts out 1.95 J of light energy, and the compact fluorescent bulb puts out 30 J. a) What is the efficiency of each bulb? b) What would be the advantages of making a bulb more efficient? 7. Consider the list of energy conversions & their efficiencies on p. 127 of your text. a) Rank the 3 product forms of energy (light, heat, mechanical) from most to least efficient to produce. You’ll have to generalize. b) Can you explain why your answer for (a) might be logical/expected? Sc 9: Machines & Mechanical Advantage Name___________________ Formulae to know: M.A. = FL / FE, FL x dL = FE x dE 1. A 61.2kg block is pulled up a ramp. The force required to do this is 200N. a. What force would be needed to lift the block? b. What is the mechanical advantage? c. What is the function of the machine? 2. A 5kg block is pushed up a ramp with a force of 7N until it reaches a height of 2m. a. What is the load force of the block? b. How long is the ramp? 3. A 500N block is placed on one end of a lever. A force of 200N is applied to the other side. a. What is the mechanical advantage? b. If you push the right side of the plank down by 50cm, how far will the block be lifted? c. What is the function of this machine? 4. A lever is used to lift a 9,000,000 N car with a 2,178,000 N applied force. a. What is the mechanical advantage? b. How far must you move the free end of the lever in order to lift the car 50cm off the ground? 5. To lift a 10 N object with your hand/arm, a 35 N force is applied by muscles near your elbow to lift your entire arm. This is an example of a 3rd class lever. a. What is the mechanical advantage? b. If your arm moves 9 cm near the elbow, what distance will your hand move? c. What is the machine function of your arm? 6. A 400N child and his 350N friend are playing on the see-saw. If the 400N child sits 80cm from the centre of the see-saw, where will his friend need to sit to balance it? 7. A girl pushing a load in a wheelbarrow is able to exert an upward force of 140N on the handles. The load is 25 cm from the wheel, and the handles are 75 cm from the wheel. a) Draw a diagram of this lever: b) What maximum load can she carry in Newtons and in kg? Levers Worksheet Name___________ The fulcrum is between the The effort force is between The load force is between the effort force and the load the load force and the effort force and the fulcrum. force. fulcrum. Function: Function: Function: Identify which classes of levers are being used in each of the following machines: Scissors __________________________________________ Tweezers __________________________________________ Wheelbarrow __________________________________________ Nut cracker __________________________________________ See Saw __________________________________________ 3-hole punch __________________________________________ Pliers __________________________________________ Stapler ___________________________________________ Fishing Rod _________________________________________ Science 9 - PULLEYS Name:______________ In each of the following pulley systems, the load force is 10 N and the load force moves 0.1 metre. Calculate the effort force, effort distance, mechanical advantage, number of support strings, and function of each of the systems, then fill in the data table on the following table. A. B. C. Effort Force Effort Effort Force Force Load Load Force Load Force Force D. E. F. Effort Force Effort Force Effort Force Load Force Load Load Force Force SYSTEM A SYSTEM B SYSTEM C SYSTEM D SYSTEM E SYSTEM F Effort Force (N) Effort Distance (m) Mechanical Advantage Number of Support Strings Function: multiply force multiply distance change direction transfer energy FORCE, WORK AND MACHINES PROBLEMS - ANSWERS - 1. How much force is needed to lift: (a) a 1 kg bag of apples? 10 N (b) a single 100 g apple? 100 g / 1000 g x 10 N / 1 kg = 1 N (c) a 100 kg box of apples? 10 kg x 10 N / 1 kg = 100 N 2. Calculate the work done when a student exerts a force of 400 N to push a stalled motorcycle from a busy highway onto a quiet street, a distance of 500 m. W = F x d = 400 N x 500 m = 200 000 Nm = 200 000 J 3. A teenager’s hand moves an average distance of 7 cm while lifting the pull tab on a can of juice. The average force exerted on the tab is 8 N. How much work must the teenager do to open ten cans of juice? W = F x d = 8 N x 0.07 m = 0.56 Nm = 0.56 J 4. A hiker places a 12 kg backpack on the ground in order to open the door of a cabin. (a) How much force is required to pick up the backpack again? F = 12 kg x 10 N/1 kg = 120 N (b) How much work must be done on the backpack to raise it from the ground to the floor of the cabin, a distance of 0.3 m? W = F x d = 120 N x 0.3 m = 36 Nm = 36 J 5. Four movers have to raise identical crates onto the back of a truck 1.2 m high. The first mover lifts the 850 N crate straight up and onto the truck. The second mover uses a 4 m ramp and exerts a force of 285 N. The third mover uses a very long ramp of 10 m and exerts a force of 140 N. The fourth mover tries to lift the crate but fails. (a) Which mover exerts the largest force? Mover 1: F = 850 N; Mover 2: F = 285 N; Mover 3: F = 140 N; Mover 4: F = less than 850 N Therefore, Mover 1 exerts the largest amount of force. (b) Which mover does the most work? Mover 1: W = F x d = 850 N x 1.2 m = 1020 J; Mover 2: W = 285 N x 4 m = 1140 J; Mover 3: W = 140 N x 10 m = 1400 J; Mover 4: W = 850 N x 0 m = 0 J Therefore, Mover 3 does the most work. (c) Which mover does the least work? Mover 4 does the least work because he does not move the object. 6. A crane lifts a 500 kg box 10 m in the air. How much work is done? 500 kg = 5000 N therefore W = F x d = 5000 N x 10 m = 50 000 Nm = 50 000 J 7. An engine does 25 000 J of work lifting a 2000 N box. How far is the box lifted? d = W/F = 25 000 Nm / 2000 N = 12.5 m 8. Four students run up a set of stairs 4 m high. The table below shows their weights and times. (a) Which student exerts the largest force? Student B at 800 N (b) Which student does the least work? Student A: W = F x d = 450 N x 4 m = 1800 J An inclined plane is used to push a 500 N load to the bed of a truck, a height of 2.0 m. The sloping surface is 10.0 m long, and the mover pushes with an effort force of 100 N. (a) Calculate the work output (work done by machine on load). W = F x d = 500 N x 2.0 m = 1000 Nm = 1000 J (b) Calculate the work input (work done on machine by mover). W = F x d = 100 N x 10.0 m = 1100 Nm = 1100 J (c) Calculate the efficiency of the machine. Efficiency = work output/work input x 100% = 100 J / 1100 J x 100% = 91% 10. A screw-type pump is used to raise 200 kg of water a distance of 3.0 m. The handle of the pump is turned with an effort force of 40 N a total of 1200 times, tracing a circle of 20 cm circumference each time. (a) Calculate the work output. W = F x d = 2000 N x 1.0 m = 6000 Nm = 6000 J (b) Calculate the work input. W = F x d = 1200 x 40 N x 0.2 m = 9600 Nm = 9600 J (c) Calculate the efficiency. Efficiency = work output/work input x 100% = 6000 J / 9600 J = 62.3% 11. A farmer uses a wheel-and-axle to raise a 1000 N feed sack to the loft of a barn, a height of 8.0 m. The handle of the wheel-and-axle must be turned 150 times to do this using an effort force of 100 N each time. On each turn, the handle traces out a circle 60 cm in circumference. Calculate the machine’s efficiency. Work Output = F x d = 1000 N x 8.0 m = 8000 Nm = 8000 J Work Input = 150 x F x d = 150 x 100 N x 0.6 m = 9000 Nm = 9000 J Efficiency = work input/work output x 100% = 8000 J / 9000 J x 100% = 88.9% SIMPLE MACHINES FLOWCHART defined as functions defined as to does SIMPLE 6 work types MACHINE functions 5 functions to made up of does work functions to made up of functions to defined as 3 types functions to function to amount multiplied determines defined as 3 types calculated by functions to functions to functions to SIMPLE MACHINES FLOWCHART INSTRUCTIONS: Complete the Simple Machine flowchart by cutting and pasting the terms below into their correct places. Add in your own examples. a sloping surface screw fulcrum is between effort along which a load force and load force is moved transfer energy inclined plane from one form to by being pushed another large diameter disk firmly into another object attached to a small load force diameter shaft effort force movabl mechanical a device that helps effort force is between multiply force advantage people do work load force and fulcrum more easily multiply force or multiply fixed multiply force distance or speed transfer forces from one place to wedge wheel and axle a rope or cable that is another looped around a wheel change the multiply force lever direction of the multiply speed or force distance load force is between lift heavy loads effort force and fulcrum multiply distance & speed multiply force an inclined by moving into or combination plane through an object wrapped multiply force around a rod change direction a bar that is supported at multiply force one point (fulcrum) pulley ANSWERS a device that helps defined as a sloping surface people do work inclined plane along which a load more easily is moved functions to multiply force defined as does by being pushed SIMPLE 6 wedge work into another object types MACHINE functions to multiply force an inclined 5 functions plane made up of wrapped transfer forces by moving into or around a rod does from one place to screw work through an object another functions to multiply force transfer energy from one form to large diameter disk firmly made up another wheel and axle of attached to a small diameter shaft functions to multiply force or multiply change the distance or speed direction of the force defined as a rope or cable that is pulley looped around a wheel multiply speed or 3 types fixed movable combination distance functions to function to multiply force change direction multiply force amount multiplied determines defined as a bar that is supported lever at one point (fulcrum) mechanical 3 types advantage calculated fulcrum is between effort load force is between effort force is between by force and load force effort force and fulcrum load force and fulcrum load force functions to functions to functions to effort force lift heavy loads multiply force multiply distance & speed Sc 9 Forces Worksheet Name__________ FORCES FLOWCHART defined as affected by occurs when opposed or opposed by aided by needed to units measured in FORCE defined as when it moves an object through a distance amount done depends on the formula for work is units measured in can be equated to INSTRUCTIONS: Use the following boxes to fill in the flowchart on the previous page. Either copy them out or cut and paste them. mass of objects and the attraction the distance Joules (J) distance between between all object moves objects objects friction Newton (N) make an object move one material rubs against the surface gravity of another Work is done 1 J = 1 N .m amount of Work = Force x distance force exerted a push or a pull FORCES FLOWCHART ANSWERS the attraction mass of objects and one material rubs between all distance between against the surface objects objects of another defined as affected by occurs when opposed or make an opposed by gravity friction aided by object move needed to Newton (N) units measured in FORCE defined as a push or a pull when it moves an object through a distance Work is done amount done depends on amount of the distance force exerted object moves the formula for work is Work = Force x distance units measured in Joules (J) can be equated to 1 J = 1 N .m PHYSICS 9 - Review Name_________________ FORCES…(Chapter 5) o Pushes and pulls are called forces. Examples of forces are gravitational force, pushing and pulling on an object, centripetal force (the force that pushes an object outward from a centre of rotation), and the force of friction. o The newton (N) is the unit used to measure force. o 1 kg = 10 N (because F = ma and the acceleration due to gravity is 9.8m/s2, so F = 1kg x 9.8m/s2 = 9.8 N – so we just say 10N) o Gravity is the force any object exerts on every other object. o Mass is the amount of matter in an object. The force of gravity on you depends on: (a) your mass, (b) the mass of the object attracting you, and (c) how far away you are from the object attracting you. o Friction is the force that resists motion whenever one material rubs against another. In other words, it is the force that tries to stop anything from moving. Any time there is friction, some mechanical energy is transformed to thermal energy. A lubricant is any material that can be used to decrease friction. WORK… (Chapter 5) o If we exert a force on something and move it, we are doing work. The amount of work done is calculated by multiplying the force exerted (in Newtons) by the distance the object is moved (in metres). Work = force x distance. A joule is the unit used to measure work done or energy transformed. (1 joule = 1 newton metre) The amount of work done is equal to the amount of energy transformed. WORK = FORCE x DISTANCE (Force – Newtons, distance = m, work = Nm = J) You writing notes, although you think you are doing a lot of work, are actually doing very little, as your pencil is moving only a small distance! MACHINES… o Simple machine - anything that makes it easier or more convenient to do work. Three ways a simple machine can do this is by: 1. Multiplying a force ex. a car jack allows you to lift a car with less force 2. Multiplying speed ex. Bicycle pedals require less distance to be pushed than the distance the tire turns in one revolution 3. Changing the direction of a force ex. A flag can be lifted up a flagpole by pulling down. The number of times a machine can multiply effort force is the mechanical advantage: MA = load force (FL)/effort force (FE) o The six types of simple machines are: Inclined plane; wedge; screw; lever; pulley; wheel and axle o With a simple machine, you always make work easier and more convenient, but you do not do less work, you actually end up doing a tiny bit extra, here’s why… The work done by a machine when it moves a load is called its work output WL = FL x dL The work done on a machine is called its work input WE = FE x dE Efficiency of a machine = (work output of a machine) / (work input to a machine) x 100% 19-1 Chapter 19 - Assignment #1 Doing Work with Machines 1. What is a machine? Give an example of a machine. (pg 418) 2. List the 5 functions of a machine. (pg 419) Also, give 3 examples of machine functions (pg 420, left side) 3. What is mechanical advantage? (pg 420) 4. Give the equation for mechanical advantage. (pg 420) 5. Explain what load force is and what effort force is. (pg 420) 6. Why does a ramp seem like getting something for nothing, but is really not the case. (pg 420) 7. What is true for all simple machines? (pg 420) 8. Name the 6 simple machines. (pg 422, top) 9. What is a ramp? (pg 422) 10. What happens when the slope gets more gentle? (pg 420) 11. What is the function of an inclined plane? (pg 422) 12. What is a wedge and what is itsÕ function? (pg 423) 13. How can you make the mechanical advantage of a wedge greater? (pg 423) 14. Give 4 examples of wedges. (pg 423) 15. What is the simple machine called the screw and what is its function? (pg 423) 16. What is a lever? (pg 424) 17. Draw a diagram to show how the forces can be arranged in the 3 types of levers and give an example of each of these types of levers. (pg 424 and 425) 18. Give an example where levers are used in pairs. (pg 425) 19. What is wheel and axle? (pg 426) 20. Draw a diagram of a wheel and axle. (pg 426) 21. What do wheel and axles do? (pg 425) 22. What is a pulley? (pg 427) 23. What are the 3 types of pulley systems and what is the function of each? (pg 427) 24. Draw a diagram of each of the 3 types of pulley systems. (pg 427) 25. Read pg 430. How are robots simple machines? (pg 431) 26. What must extra force be used to overcome in simple machines? (pg 431) 27. What is the efficiency of a machine? (pg 431) 28. State the 2 ways of calculating efficiency using equations. (pg 431) 29. What would be the efficiency of a machine with no friction? (pg 431) 30. How does work output in real machines compare to work input? (pg 431) 31. Why can machines not create work? (pg 432) ENERGY… (Chapter 6) An object has energy if it can make other objects move. Energy is the ability to make things move o Ex. Magnets on paper clips o Tuning fork on water o Flowing water o Rolling carts o Rubber bands If you lift your backpack weighing 20 N a height of 1 m to your shoulders, your backpack now has an additional 20N x 1m = 20Joules of potential energy stored which later can be used to do work o The Law of Conservation of Energy says “Energy cannot be created or destroyed. It can be changed from one form to another, but the total amount of energy in the universe never changes. Ex. How much energy is needed to raise the a load of 4000kg a distance of 300m? State the answer in kJ. 1. Change the mass to newtons 2. Calculate the work done 3. Determine the amount of energy required to do the work 4. Change the energy units to kilojoules (1000J = 1kJ) Types of Energy • Mechanical: the kind of energy an object has because it is moving • Gravitational: the kind of energy an object has when it is in position to roll, fall or slide downhill • Chemical: the energy that is stored in chemical compounds, such as gasoline, wood, coal, dynamite, and batteries • Magnetic: the form of energy that causes some kinds of metal to attract or repel some metal objects • Electrical: the energy of moving electrical particles • Thermal: the energy an object has because its particles are moving in all directions • Light the form of energy that you can see • Elastic the energy stored in an object whose shape is changed by stretching, compressing, or twisting • Nuclear the energy stored in the central part of the atom • Sound the kind of energy that is produced when an object vibrates; energy that you can hear Potential and Kinetic Energy Energy can be classified in two ways: 1. Potential Energy – Stored energy • Wound up spring in a toy car which gets transformed into mechanical energy • A battery has stored chemical energy 2. Kinetic Energy – the energy of anything in motion (kinetic means moving) • A moving car • A roller coaster Gravitational, chemical, magnetic, electrical, elastic and nuclear are considered forms of potential energy or energy which can be stored. Mechanical, thermal, light and sound are forms of kinetic energy or energy which cannot be stored. Energy Transformations: Transformation of energy occurs when energy is changed from one form to another. Device Input energy Output energy 1. Candle 2. Drill 3. Generator 4. CD player 5. Flashlight o An energy converter is any apparatus that changes one form of energy into another. Energy converters change some energy into thermal energy through friction. o Efficiency of an energy converter refers to the converter’s ability to transform large amounts of the original energy into useful energy. Efficiency can be calculated by: useful energy output Efficiency = x 100% total energy input Do activity 6D - Energy flow through a car ANSWERS to Fill in the table below: Device Input energy Output energy 1. Candle Chemical Thermal, light 2. Drill Electrical Sound, mechanical 3. Generator Mechanical Light, electrical 4. CD player Electrical, Chemical Mechanical, sound 5. Flashlight Chemical Light, Electrical HEAT – (Chapter 7) Thermal Energy and Temperature • Thermal energy is heat • Heat and temperature are not the same thing. Heat or thermal energy is the total energy of all the particles in an object • Depends on the size of the object, a pot of hot soup has more energy than a cup of hot soup Temperature is a measure of the speed of the particles • Temperature does not depend on the size of the object, a cup and a pot of soup have the same temperature • Low temperature – slow moving particles • High temperature – fast moving particles • Thermometers measure temperature, either mercury or coloured alcohol o The Fahrenheit thermometer measures water freezing at 32o F o The Celsius thermometer measures water freezing at 0o C Heat Transfer • Heat transfer involves the movement of heat from a hot object to a cold one • Conduction – Heat transfer in solids o A conductor is a substance that transfers heat well by the collision of particles (many metals are excellent conductors) • Convection – Heat transfer in fluids o Fluids are liquids and gases that are poor heat conductors because particles are too far apart o Hot fluids rise • Radiation – Heat and light come to us from the sun through empty space where there are no particles – energy that is transferred without particles is called radiant energy o Dark objects absorb energy well • Preventing heat transfer – In order not to lose heat, o Insulators – slow down or prevent heat transfer – like in a thermos The Kinetic Molecular Theory Name:_____________ Date:________ Per:___ _____________ means moving _____________ are particles of matter _____________ is used to explain observations The kinetic molecular theory explains our observations of moving particles of matter There are eight statements in the KMT: 1. All ___________ (solid, liquid & gas) is made up of tiny particles. 2. These particles are in constant _______________. This means they have kinetic energy or “_______________” motion. 3. There are _____________ between the particles of matter. 4. The particles and spaces are so ______________ that they cannot be seen. 5. In a ____________, the particles are very close together, and the spaces between the particles are small. Particles of a solid can not move very fast, but can only vibrate. 6. In a ____________, the particles are slightly farther apart, because the spaces between the particles are larger. Liquid particles move slightly _________ than solid particles. 7. In a ___________, the particles are very far apart. The spaces between the gas particles are very large. Gas particles move very ____________. 8. If ______________ is added to matter, the particles gain kinetic energy, and so they can move faster The Kinetic Molecular Theory Name:____KEY________ Date:________ Per:___ ____Kinetic____ means moving ____Molecules__ are particles of matter ____A Theory__ is used to explain observations The kinetic molecular theory explains our observations of moving particles of matter The KMT is a revised version of the particle model of matter. It explains the movement (and not just the arrangement) of the particles in a solid, liquid or gas. It explains what happens when heat is added to matter There are eight statements in the KMT: 1. All ___matter________ (solid, liquid & gas) is made up of tiny particles. 2. These particles are in constant ___motion_________. This means they have kinetic energy or “___moving_________” motion. 3. There are ______spaces_____ between the particles of matter. 4. The particles and spaces are so ____small____ that they cannot be seen. 5. In a ___solid_______, the particles are very close together, and the spaces between the particles are small. Particles of a solid can not move very fast, but can only vibrate. 6. In a __liquid____, the particles are slightly farther apart, because the spaces between the particles are larger. Liquid particles move slightly _faster______ than solid particles. 7. In a __gas_______, the particles are very far apart. The spaces between the gas particles are very large. Gas particles move very __fast________. 8. If ___heat____ is added to matter, the particles gain kinetic energy, and so they can move faster POWER…(Chapter 7) Power is the rate at fwhich energy is produced, absorbed or transferred. POWER = ENERGY / TIME (Energy – Joules, time - sec, Power – J/s = Watt) o The power of an energy converter refers to how much work it can do in one second. o The unit for measuring power is the watt. o (1 watt = 1 joule/second) Ex. In two minutes, an electric kettle transfers 144 000 J of energy to the water in it. What is the power of the kettle? Do the following conversions: 144 000J = __________kJ 48 000 W = ___________ kW 120 kJ = __________ J 4.2 J/s = ___________ W 1.2 kW = _________W 8.4 x 103 W = __________kW Power and Heat Worksheet Name:_________________ Date:_________ Per:_____ 1. What is the difference between thermal energy and heat? 2. Determine the power of each of the following electrical appliances. a) The output of a laser is 0.05J every 100 seconds. b) A curling iron uses 48000 J of energy per minute c) An electric light bulb uses 2.16 x 105 J of energy in one hour. 3. Determine the amount of energy transformed or used in each case a) A 2000 W electric pencil sharpener operates for 3.0 seconds b) A 1200 W kettle heats water for 5.0 seconds c) A 100 W stereo is operated for 1 hour. Heat Capacity o The amount of heat required to change the temperature of an object. o It is an object’s “capacity” or “ability” to gain or lose heat Eg. Apple pie filling – filling remains hotter than the crust. Specific Heat Capacity o The amount of heat transferred when the temperature of 1.0kg of a substance changes (inc or dec) by 1.0o C o SHC is used to compare substances o Take equal masses of two materials, heat them up, and determine the rate at which the heat is transferred o This can be used to identify matter (See SHC chart on page 150) How to calculate SHC: SHC = Energy/(mass x change in temperature) E E= m= SHC = m x ∆T ∆T = SHC = Sand vs. water at the beach…. (Pg. 150) Sand has _________ and water has ______________ Sand holds heat for a _________ time water holds heat for a __________ time Sand takes a ________ time to heat up, water takes a _________ time to heat up High Heat Capacity Different materials take different amounts of heat to raise a given mass of the material the same temperature change. Water has a high SHC, and thus water can absorb a large amount of energy. It takes a long time to heat up and a long time to cool down. The SHC of Water: 4200 J/kg oC or 4.2 kJ/kg oC This means it takes __________ J of energy to increase the temperature of _______ kg of water by ________ o C Or, if ______ kg of water was cooled by _______ oC, then it would release _________ J of energy Heat Transfer Heat is a form of energy. It used to be thought that it was a type of matter called “caloric” that flowed into cold objects. We now know that heat is ENERGY. Law of Conservation of Energy Energy can not be created or destroyed, it can only change form. Do page 151 # 1-3 Changes of State Draw a warming curve on the graph below (see pg 156). Make sure to fully label the diagram Define: Latent heat - Latent heat of fusion - Latent heat of vaporization -

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