Honors Physics Dr.Darmanyan HOMEWORK ASSIGNMENTS HW for Unit I HW 1.1. Indicate whether each of the following changes is chemical or physical. Explain. a. Leaves change color in autumn. b. Crushing a dry leaf in your hand. c. An aspirin dissolves in your stomach. d. An aspirin acting in the body to relieve a headache. e. Beans cooking f. Grass growing g. Grass cutting h. Bleaching clothes HW 1.2. a. Calculate the average speed (km/h) of Charlie, who runs to the store 4 km away in 30 min. b. Calculate the distance (km) that Charlie runs if he maintains this average speed for 1 hour. HW 1.3. An object is dropped from the rest and falls freely. After 6 s, calculate its instantaneous speed, average speed, and distance fallen. HW 1.4. Calculate the resultant of the pair of 100 km/h velocity vectors that are at right angles to each other. HW 1.5. Neglecting air resistance, if you throw a ball straight up with a speed of 20 m/s, how fast will it be moving when you catch it? HW for Unit II HW 2.1. Does a 2-kilogram bunch of bananas have twice as much inertia as a 1-kilogram loaf of bread? Twice as much mass? Twice as much volume? Twice as much weight, when weighed in the same location? HW 2.2. Consider what would happen if you suspended a 10-N object midway along a very tight, horizontally stretched guitar string. Is it possible for the string to remain horizontal without a slight sag at the point of suspension? HW 2.3. If a car can accelerate at 2 m/s2 , what acceleration can it attain if it is towing another car of equal mass? HW 2.4. If a heavy person and a light person open their parachutes together at the same altitude and each wears the same size parachute, who will reach the ground first? HW 2.5. Some people used to think that a rocket could not travel to the moon because it would have no air to push against once it left the Earth’s atmosphere. Now we know that idea was mistaken. What force propels a rocket when it is in a vacuum? HW 2.6. Suppose you exert 200 N on your refrigerator and push it across the kitchen floor at constant velocity. What friction force acts between the refrigerator and the floor? Is the friction force equal and opposite to your 200-N push? Does the friction force make up the reaction force in your push? HW for Unit III HW 3.1. If you replace the regular tires on your car with tires of larger diameter, how will your speedometer reading differ? Explain. HW 3.2. When a soaring eagle turns during its flight, what is the source of the centripetal force acting on it? HW 3.3. Why does a washing machine vibrate violently if the clothes are not evenly distributed in the tab? HW 3.4. When you carry a heavy load (such as a pail of water) with one arm, why do you tend to hold your free arm out horizontally? HW 3.5. If you know your own weight and have a seesaw and a meterstick available, how can you determine the approximate weight of a friend? HW 3.6. Consider two rotating bicycle wheels one filled with air and the other filled with water. Which would be more difficult to stoop rotating. Explain. HW for Unit IV HW 4.1. Calculate the force of gravity between the Earth (mE = 6.0 x 1024 kg) and the Sun (mS = 2.0 x 1030 kg). The average Earth-Sun distance is 1.5 x 1011 m. HW 4.2. By what factor would your weight change if the Earth’s diameter were doubled, and its mass were also doubled? HW 4.3. Half way to center of the earth, would gravity pull on you more strongly or less strongly than at the surface of the Earth? HW 4.4. What would be the effect on Earth’s tides if the diameter of the Earth were larger that it is? The earth were as it presently is , but the Moon were larger – with the same mass? HW 4.5. Why does the force of gravity change the speed of a satellite when it is in an elliptical orbit, but not when it is in a circular orbit? HW for Unit V HW 5.1. A car with a mass of 1000 kg moves at 20 m/s. What braking force is needed to bring the car to a halt in 10 s? HW 5.2. If you topple from your tree house, you will continuously gain momentum as you fall to the ground below. Does not this violate the conservation of momentum? HW 5.3. Imagine that you are hovering next to the space shuttle in an Earth-orbit and your buddy of equal mass who is moving at 4 km/h with respect to the ship bumps into you. If he holds onto you, how fast do you both move with respect to the ship? HW 5.4. Which requires more work, sliding a 10-kg load on the floor a distance of 2 m, or sliding a 5-kg load a distance of 5 m. HW for Unit VI HW 6.1. For the metals listed, the number of atoms per unit cell is given in parentheses. What type of cubic lattice does each metal form? a. Po (1) b. Fe (2) c. Ag (4) HW 6.2. Of the five major types of crystalline solid, which would you expect each of the following to form and why? a. Ni b. F2 c. CH3 OH d. Na2 SO4 e. SF6 HW 6.3. If you use a batch of cake batter for cupcakes instead of a cake and bake them for the time suggested for baking a cake, what will be the result? HW 6.4. Consider a model steel bridge that is 1/100 the exact scale of the real bridge that is to be built. a. If the model bridge weighs 50 N, what will be the real bridge weight? b. If the model bridge doesn’t appear to sag under its own weight, is this an evidence that the real bridge will not appear to sag either? HW 6.5. Discuss, how the properties of iron are modified in producing the various types of steel. HW 6.6. A piece of aluminum house siding is 3.66 m long on a cold winter day (-28o C). How much longer is it on a very hot summer day (39 o C)? HW 6.7. An aluminum soft-drink can, 354 mL, is filled to the brim with water in the refrigerator (4.4 o C). How much liquid will spill? UNIT VII. LIQUIDS Lesson 7.1. The Fluids. HW 7.1. Lesson 7.2. CWA 7.1. Liquid Pressure. HW 7.2. Lesson 7.3. CWA 7.2. Buoyancy. HW 7.3. Lesson 7.4. CWA 7.3. Immersing and Floating. HW 7.4. Lesson 7.5. CWA 7.4. Hydrostatics. HW7.5. Lesson 7.6. CWA 7.5. Surface Tension. Hydrodynamics. Vocabulary Quiz. HW 7.6 Lesson 7.7. Pre-test. Lesson 7.8. Test # 7. HW for Unit VIII HW 8.1. Explain, why air pressure does not crush your body? HW 8.2. Complete the lab repot :Boyle’s Law.” HW 8.3. A balloon that weighs 1 N is suspended in air, drifting neither up nor down. How much buoyant force acts on it? What happens if the buoyant force decreases? HW 8.4. If you take a barometer outside on a windy day, will it give a lower reading than if you keep it indoors? Explain. HW 8.5. a) How does a plasma differ from a gas? b) Site at least three examples of plasma in your daily environment. HW for Unit IX HW 9.1. a. A 0.52-kg bird flying at an altitude of 550 m. What is its gravitational potential energy? b. A 1500-kg car is moving at the speed of 18 m/s. What is its kinetic energy? HW 9.2. You tell your friend that no machine can possibly put out more energy than is put into it, and your friend states that a nuclear reactor puts out more energy that is put into it. What do you say? HW 9.3. In rising a 5000-N piano with a pulley system, the workers note that for every 2 m of rope pulled down, the piano rises 0.4 m. a) Ideally, how much force is required to lift the piano? b) If the workers actually pull with 2500 N of force to lift the piano, what is the efficiency o the pulley system? HW 9.4. Compare the mechanical advantage of a long, thin wedge with that of a short, wide wedge. Which is greater? HW for Unit X HW 10.1. a. Explain how energy is different from work. c. Explain the difference between potential energy and kinetic energy. d. List three forms of energy that do not be long to mechanical energy. HW 10.2. Identify types of energy change in the following: The book was taken from the floor and placed on the table. The ocean water is heated by the Sun. The gasoline is burned in the car engine. An electrical heater warms the room. A bomb explodes. HW10.3. Convert the following temperatures to both degrees Fahrenheit and Kelvins: a. the boiling point of liquid hydrogen (-252.87o C). b. the melting point of gold (1064o C). HW 10.4. Why is water a very useful cooling agent for the automobiles and other engines? HW10.5. How much heat should be added to 55 g of paraffin to increase its temperature from 20o C to 65o C? HW for Unit XI HW11.1. Why does the temperature of hot chocolate decreases faster if you place a metal spoon in the liquid? Use the scientific terms in your explanation. HW 11.2. A 25- g sample of a metal at 75o C is placed in a calorimeter containing 25 g of water at 20o C. The temperature stopped changing at 29.4o C. What is the specific heat of the metal? What is the name of the metal? HW 11.3. Why does the high specific heat of water have to do with convection currents in the air at the seashore? HW 11.4. Is it more efficient to paint a heating radiator black or silver? Explain. HW for Unit XIII HW 13.1. Describe a situation that demonstrates that water waves carry energy. HW.13.2. Describe three types of waves. HW.13.3. The wave shown in the figure below has a period of 3 s. Find the following values for this wave: a. amplitude b. wavelength c. frequency HW.13.4 The speed of sound in air is about 340 m/s. What is the wavelength of a sound wave with a frequency of 220 Hz? HW.13.5. Explain why you can hear two people talking even after they walk around a corner. HW for Unit XIV HW 14.1. Calculate the wavelength of ultrasound used in medical imaging if the frequency is 15MHz. The speed of ultrasound waves is 1500 m/s. HW 14.2. As the distance to the bottom of the ocean is 1580 m, how long does it take for the sound to reflect using sonar? The speed of ultrasound in water is 1490 m/s. HW 14.3. If you hear a train whistle pitch drop as the train passes you, can you tell from which direction the train was coming? Explain. HW for UNIT XV HW 15.1. State one piece of evidence supporting the wave model of light and one piece of evidence supporting the particle model of light. HW 15.2. Explain why people can see the light but cannot hear the sound on the surface of the Moon. HW 15.3. Name the regions of the electromagnetic spectrum from the shortest wavelength to the longest wavelength. HW 15.4. Explain how a plane mirror forms a virtual image. HW 15.5. If you were spearing a fish with a spear, would you aim above, below, or directly at the observed fish to make a direct hit? What would by your answer if you use a laser light to “spear” the fish? HW for Unit XVI HW 16.1. If an electron at a certain distance from a charged particle is attracted with a certain force, is the charged particle in this case positive or negative? Explain. HW 16.2. a. Why are metals good conductors? b. Why are both rubber and glass good insulators? HW 16.3. If an electron at a certain distance from a charged particle is attracted with a certain force, how will the force change if the distance between these two particles increases by the factor of 2? Explain. HW 16.4. Draw the picture representing magnetic field. Indicate the area with the greatest strength of magnetic force. HW 16.5. Why do some pieces of iron behave as magnets, and other pieces of iron do not? HW for UNIT XVII HW 17.1. You can get a sunburn of a sunny day and an overcast day. But you cannot get a sunburn if you are behind glass. Explain. HW 17.2. a) Why do we not list black and white as colors? b) Why are the interiors of optical instruments black? HW 17.3. Discuss the difference, in terms of reflection, between objects that appear blue and objects that appear yellow. HW 17.4. What colors of ink do color ink-jet printers use to produce the colors you see. Do the inks form colors by color addition or by color subtraction? HW 17.5. Very big particles, such as droplets of water, absorb more radiation than they scatter. How does this fact help to explain why rain clouds appear dark? HW for Unit XVIII HW 18.1. Why does the temperature at which a liquid boils depend on atmospheric pressure? HW 18.2. Air-conditioning units contain no water whatsoever, yet it is common to see water dripping from them when they are running on a hot day. Explain. HW 18.3. Explain why on the snow day the air temperature is higher than on clear day. HW 18.4. How much heat is transferred when 25.0 g of ethyl alcohol vapor condenses to form a liquid alcohol? Is energy absorbed or released?