What is a simple machine, What is a lever? What are some examples of a lever? How do levers help to make our lives easier? How does a pulley work? What is a simple machine, What is a lever? What are some examples of a lever? How do levers help to make our lives easier? A pulley is a simple effective machine. It is a small wheel with a grooved rim. In order for the pulley to work, a rope, belt or chain is wrapped around a small wheel so that heavy objects can be lifted by pulling on the other end of the rope, belt or chain. A pulley changes the direction of the force, making it easier to lift things up to high-rise areas. There are three types of pulleys: a fixed pulley, a movable pulley and a combined pulley. In order for a pulley to work, it needs to be secured onto an elevated structure. Following this, the pulley can lift up the heavy load when one end of the rope is pulled. Consequently, heavy objects are manoeuvred into other desired positions. Pulleys are very useful machines so as a result, they are commonly used in mechanical workshops to lift heavy objects. They are also used in cranes for loading cargo onto ships and in wells to retrieve buckets. My Science Who would write an explanation? Journal Why would people write an explanation? Who would read an explanation? Where would you find an explanation? What do you talk about in an explanation? When might someone be involved in an explanation? What do you need to include in an explanation? What is an explanation? Find the answers to the following questions using the websites below. http://www.mikids.com/Smachines.ht m http://www.beaconlearningcenter.co m/Weblessons/SimpleMachines/machin es002.htm 1. 2. 3. 4. 5. What is a simple machine? What is a lever? How does a lever work? Name 3 examples of a lever. Choose one of these examples and explain how it works. 6. Draw a labelled diagram of a lever. 7. What is a wedge? 8. How does a wedge work? 9. Name 3 examples of a lever. 10. Choose one of these examples and explain how it works 11. Draw a labelled diagram of a lever. Lesson Five Listening Activity – Teacher Copy Listening Activity Building the field 1. A lever is a simple machine made with a straight bar that moves on a fixed point called a fulcrum. 2. All levers have two parts, the bar and the fulcrum. 3. The longer the lever is, the less force will be needed to move the load. 4. The load and the force move in opposite directions. 5. Notice that as the hammer is pulled down, the nail moves up. 6. A wedge is made by putting two inclined planes together. They come together to form a Vshape. 7. A wedge may be used to lift or pry apart heavy objects. 8. A wedge can also be used to stop an object from moving. 9. A wedge has only one part. 10. The force and the load move in different directions. Lesson Five Listening Activity – Student copy Listening Activity Listen to the text and record three pieces of information you heard. Record any new or unfamiliar technical language you heard. Draw the simple machines that are being described. Lesson Six/seven Listening Activity Listening Activity Lesson Six Topic: How does a can opener work? Record the main instructions of how to use a can opener. http://www.youtube.com/watch?v=AfLB10D7s3U Listening Activity Lesson Seven Topic: How does a can Technical Language opener work? Record the main instructions of how to use a can opener. http://www.youtube.com/watch?v=pKrq72EXEWg&feature=fvw Technical Language Lesson Eight Listening Activity Listening Activity a grasping Defining Technical tool having a pair of jaws and handles pivoted Language together to work in opposition. to turn (something) from one direction to another, as by rotating or revolving a line or border at which a surface ends the side of a can that the can opener attaches to Twist Click Horizontal Resistance Lip Crimping flat or level, parallel to ground level. Unhook Pinchers Secure Release Edge to let go to detach, unfasten or open by undoing a hook to press into small regular folds; make wavy. a force that tends to go against motion Lesson Eight Talking Activity ist Horizontal Resist Crimping ip Unho hers Twist Lip Pinchers Horizontal R Crimping Lesson Nine Listening Activity – teacher copy How a Can Opener Works Listening Activity 1. To begin, a can opener placed on the rim of a can. is 2. As soon as the handle is pushed down, the blade of the cutter punches a hole in the rim of the can. 3. At this point, the handles are squeezed and the wheel and the cutter grip it. They are specially shaped pieces of metal that act like a lever. 4. During this stage, the handles are attached to a fulcrum at one end. 5. The cutter has a sharp blade that punches a hole in the can and as the key turns the toothed wheel, the cutter goes around the rim of the can and acts like a wedge. 6. When the turn key is turned, the toothed wheel turns, and then, while turning, it turns the can round. 7. The handles eventually release when the cutter has gone all around the rim of the can. 8. When the handles are released, the toothed wheel and the cutter will let go of the can. Lesson Nine/Ten Listening Activity – Student copy How a Can Opener Works Listening Activity Lesson Nine 5. 6. 7. 8. 1. 2. 3. 4. How a Can Opener Works Listening Activity Lesson Ten Step Number 1. 2. 3. 4. 5. 6. 7. Steps Time/sequence word 8. Lesson Ten Listening Activity – teacher copy How a Can Opener Works Listening Activity 1. To begin, a can opener is placed on the rim of a can. 2. As soon as the handle is pushed down, the blade of the cutter punches a hole in the rim of the can. 3. At this point, the handles are squeezed, the wheel and the cutter grip it. They are specially shaped pieces of metal that act like a lever. 4. During this stage, the handles are attached to a fulcrum at one end. 5. The cutter has a sharp blade that punches a hole in the can and as the key turns the toothed wheel, the cutter goes around the rim of the can and acts like a wedge. 6. When the turn key is turned, the toothed wheel turns, and then, while turning, it turns the can round. The turn key looks like a metal bow and the tooth wheel has jagged teeth. They both act like a wheel and an axle but the toothed wheel alone acts like a gear. 7. The handles eventually release when the cutter has gone all around the rim of the can. 8. When the handles are released, the toothed wheel and the cutter will let go of the can. Topic/Issue: Target audience: Statement of Phenomena: Langua ge of time/s equenc e Explanation Sequence Paragraph One Explanation Sequence Paragraph Two Explanation Sequence Paragraph Three Concluding Statement Lesson Twelve Writing Activity Explanation Planning Sheet Cable Lifts The most common type of lift is the cable lift, which is a much better energy spender and doesn't require intense drilling to build. A lift car is hooked up to four to eight steel cables that run over a grooved pulley at the top of the building. The cables are attached to a weight on the other side of the pulley that acts as a balancer, conserving energy so the pulley doesn't have to move much to raise or lower the lift car. A computer system is put in place that locates where the lift car is and keeps track of floor requests when buttons in the lift car or on different levels are pushed. Depending on the lift system, the computer then figures the best way to move the car as efficiently as possible to get Language of time/Sequence: Eventually, as, while, at this point, following this, during this stage. Language of cause and effect: as the handles are pushed, as a result, for this reason, until, in order for, consequently Technical Language: twist, click, horizontal, resistance, lip, crimping, unhook, pinchers, secure, release, edge everyone where they need to go. How does an lift work? When you step into an lift and close the door, you had passed through two doors and are now standing in a box (or the lift car) inside a vertical passageway (called the lift shaft). One door is in the walls of the floor that you got off, and the other door is part of the car itself. Inside the shaft are hoisting cables attached to the top of the car. The cables run over a sheave (pulley) connected to an electric motor at the top of the shaft. The other end of the cables is connected to a heavy steel weight called a counterweight. When the car goes up, the counterweight goes down; when the car goes down, the counterweight goes up. How the counterweight reduces to a minimum the power needed to operate the lift ... Weight of counterweight = Weight of the car + (about) ½ of its maximum passenger load So when the lift operates, it needs power only to lift the weight of the extra passengers in the car; the rest of the weight is balanced by the counterweight. The Cable System The most popular lift design is the roped lift. In roped lifts, the car is raised and lowered by traction steel ropes rather than pushed from below. The ropes are attached to the lift car, and looped around a sheave (3). A sheave is just a pulley with a grooves around it. The sheave grips the hoist ropes, so when you rotate the sheave, the ropes move too. The sheave is connected to an electric motor (2). When the motor turns one way, the sheave raises the lift; when the motor turns the other way, the sheave lowers the lift. Typically, the sheave, the motor and the control system (1) are all in a machine room above the lift shaft. The ropes that lift the car are also connected to a counterweight (4), which hangs on the other side of the sheave. The counterweight and the car are perfectly balanced. The purpose of this balance is to conserve energy. With equal loads on each side of the sheave, it only takes a little bit of force to tip the balance one way or the other. Both the lift car and the counterweight ride on guide rails (5) along the sides of the lift shaft. The rails keep the car and counterweight from swaying back and forth, and they also work with the safety system to stop the car in an emergency. How does a lift work? The normal lift works by several steel hoist ropes and a counterweight. The sheaves can grip the hoist ropes and move and hold the car without excessive slipping. The car and counterweights ride along vertical guide rails to keep them from swaying. The machinery to drive the lift is located in a machine room usually directly above the lift hoist way. To feed electricity to the car and receive electrical signals from it, a multi-wire electrical cable connects the machine room to the car. The end attached to the car moves with it, so the cable is called the "travelling cable." Lifts were invented in the 1800's, but back then lifts were pretty simple. There were, six spindles connecting to wires and a box. To pull it up there was a counter weight, usually a person. The very first lifts were wells!
Pages to are hidden for
"S2 Explanation simple machines resources - DOC"Please download to view full document