Physics Benchmark Exam #2 2009-2010 (Formula Sheet is on Page 10)

1. A 5-kilogram mass is lifted from the ground to a height of 10 meters. The gravitational potential energy of the mass is increased by approximately:

A 0.5 J. B 50 J. C 250 J. D 500 J.

2. What is the momentum of an asteroid that has a mass of 1.3 5 ×1012 kg and a velocity of 2.55 ×1 04/s?

A 1.89 ×10 −8 kgm/s B 5.29 ×10 7 kgm/s C 3.44 ×1016 kgm/s D 8.78 ×10 20 kgm/s

3. In collisions between two objects, kinetic energy is conserved only:

A if one of the objects was initially at rest. B if potential energy converts to work energy. C in inelastic collisions. D in elastic collisions.

4. A heated gas expands, raising a piston. Which of the following describes the energy exchanges of this process?

A Energy is transferred to the gas by the piston, and to the piston from the heat source. B Energy is transferred to the gas from the heat source, and to the raised piston from the gas. C Energy is transferred to the gas in the form of heat and work done by the piston. D Energy is transferred directly to the piston from the heat source.

5. Which mass has the greatest potential energy with respect to the floor?

A 50-kg mass resting on the floor B 2-kg mass 10 meters above the floor C 10-kg mass 2 meters above the floor D 6-kg mass 5 meters above the floor

2009-20010 Physics Benchmark Exam #2 1 6. A cup of water at 40 °C and a cup of water at 5 °C are left on a table. Which graph correctly shows the temperature of the two cups of water as time passes?

2009-20010 Physics Benchmark Exam #2 2 7. An engine has an input for heat energy of 10,750 J and does 2420 J of work. Which of the following is the heat loss?

A 0.225 J B 4,444 J C 8,330 J D 13,170 J

8. Which cart shown has the greatest kinetic energy?

9. A proposed ideal heat engine would run with a high temperature reservoir at 800 kelvin and a low temperature reservoir of 400 kelvin. When the engine is running, it extracts 400 joules of energy from the hot reservoir and does 250 joules of work each minute. How much energy is expelled to the low temperature reservoir each minute?

A 150 J B 250 J C 300 J D 400 J

10. The pressure of a gas inside a closed, rigid container will increase when the gas temperature increases. The pressure of the gas increases because the:

A density of the gas decreases B rate of collisions of gas molecules with the surface increases C container expands in size when heated D gas molecules bond together to form more massive molecules

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11. A 1.0-kilogram mass falls a distance of 0.50 meter, causing a 2.0-kilogram mass to slide the same distance along a table top, as represented in the diagram above. How much work is done by the falling mass?

A 1.5 J B 4.9 J C 9.8 J D 14.7 J

12. A basketball player who weighs 600 newtons jumps 0.5 meter vertically off the floor. What is her kinetic energy just before hitting the floor?

A 30 J B 60 J C 300 J D 600 J

13. When a gas is heated in a closed container, the internal pressure increases. Which best describes the reason for the increase in pressure?

A The average kinetic energy of the gas molecules decreases. B The potential energy of the gas increases. C The average kinetic energy of the gas molecules increases. D The potential energy of the gas decreases.

14. In which of the following processes is the order of the system increasing?

A shaking a jar containing separate layers of salt and pepper B smashing a coffee cup with a hammer C adding cold milk to a cup of hot coffee D forming crystals in a solution

2009-20010 Physics Benchmark Exam #2 4 15. A rock falls from the top of a building. It feels a downward force of 9 N, and an upward force of 5 N due to air resistance. Which statement is true about the rock’s momentum?

A It is constant. B It is undetermined. C It is changing. D It is negative.

16. A container of cold water is dumped into a larger container of hot water. It is mixed and then left alone for a long time interval. The water temperature is found to:

A randomly vary from region to region in the container. B be uniform throughout the container. C fluctuate at all positions in the container. D be greater at the bottom of the container.

17. The work done by a heat engine is equal to the difference between the heat flow:

A into the engine at a high temperature and the heat flow out at a lower temperature. B out of an engine at a high temperature and the heat flow in at a lower temperature. C into the engine at a low temperature and the heat flow out at a higher temperature. D out of the engine at a low temperature and the heat flow in at a higher temperature.

2009-20010 Physics Benchmark Exam #2 5 18. Nitrogen molecules within a glass tube are allowed to move randomly. Which figure shows the molecules in a state of greatest entropy?

19. When the speed of an object is halved, its kinetic energy is:

A quartered. B halved. C the same. D doubled.

2009-20010 Physics Benchmark Exam #2 6 20. A student throws a stone upward at an angle of 45o. Which statement best describes the stone at the highest point that it reaches?

A Its acceleration is zero. B Its acceleration is at a maximum. C Its potential energy is at a minimum. D Its kinetic energy is at a minimum.

21. Assuming there is no friction, the roller coaster car’s kinetic energy at Point X will be:

A 1,000 . B 24,525 . C 39,240 J D Cannot be determined

22. A 2.0-kilogram mass is moving with a speed of 3.0 m/s . What is the kinetic energy of the mass?

A 1.5 J B 6.0 J C 9.0 J D 12.0 J

23. Two cars having different weights are traveling on a level surface at different constant velocities. Within the same time interval, greater force will always be required to stop the car that has the greater:

A weight. B kinetic energy. C velocity. D momentum.

2009-20010 Physics Benchmark Exam #2 7 24. If the balls shown above collide in an inelastic collision and stick together, what will be the velocity of the balls after the collision?

A 5 m/s to the left B 2.5 m/s to the left C 11 m/s to the left D 15 m/s to the left

25. A child is on a sled moving down a hill at 20 meters/second. The combined mass of the sled and child is 100 kilograms. The momentum of the child and sled is:

A 5 kg m/s B 20 kg m/s C 1000 kg m/s D 2000 kg m/s

26. A high diver steps off a diving platform that is 10 meters above the water. If no air resistance is present, during the fall there will be a decrease in the diver’s:

A gravitational potential energy. B total mechanical energy. C kinetic energy. D momentum.

Boulder Cart STOP

5.0 m/s 1.0 m/s

Before Collision After Collision

27. In the above diagram, a fake boulder moving at 5.0 m/s hits a stationary cart with a mass of 1000 kg. After the collision, the boulder has stopped and the car has a velocity of 1.0 m/s. What was the mass of the boulder?

A 200 kg B 1000 kg C 2000 kg D 5000 kg

2009-20010 Physics Benchmark Exam #2 8 Open Ended:

The diagram below is drawn to a scale of 1.0 centimeter = 3.0 meters. A 650 kilogram roller coaster car starts from rest at the top of the first hill of its track and glides freely. [Neglect friction.]

A Using a metric ruler and the scale of 1.0 cm = 3.0 m, determine the height of the first hill.

B. Determine the gravitational potential energy of the car at the top of the first hill. [Show all calculations, including the equation and substitution with units.]

C. Using one or more complete sentences, compare the kinetic energy of the car at the top of the second hill to its kinetic energy at the top of the third hill.

2009-20010 Physics Benchmark Exam #2 9 2009-20010 Physics Benchmark Exam #2 10 Physics Benchmark Exam #2 2009-2010 Answer Key

1. D 500J (2b) 2. C 3.44 x 1016 kgm/s (2d) 3. C in inelastic collisions. (2e) 4 B Energy is transferred to the gas from the heat source, and to the raised piston from the gas. (3a) 5 D 6-kg mass 5 meters above the floor (2b) 6. A (3a) 7. C 8330J (3b) 8. B (2a) 9. A 150J (3b) 10. B rate of collisions of gas molecules with the surface increases. (3c) 11. B 4.9J (2.c) 12. C 300J (2c) 13. C The average kinetic energy of the gas molecules increases. (3c) 14. D Adding cold milk to a cup of hot coffee. (3d) 15. C It is changing. (2f) 16. B be uniform throughout the container. (3d) 17. A into the engine at a high temperature and the heat flow out at a lower temperature. (3a) 18. B (3e) 19. A quartered (2a) 20. D Its kinetic energy is at a minimum. (2c) 21. B 24,525J (2c) 22. C 9.0J (2g) 23. D momentum (2f) 24. B 2.5 m/s to the left (2g) 25. D 2000 kg m/s (2d) 26. A gravitational potential energy. (2c) 27. A 200 kg (2g)

Open Ended 2a/2b/2c score Criteria 2- high  Calculations are correct  Work is shown  Kinetic energy is greater at the top of the third hill 1- medium Two of the criteria are met 0-low One or none of the criteria are met

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