MULTIPLE CHOICE Circle the letter beside the BEST answer.

1. A heat engine does 800 J of work, when it takes in 1200 J of heat from the high temperature reservoir? How much heat is given to the low temperature reservoir by the heat engine?

a 800 J

b 1200 J

c 2000 J

d 400 J

e. none of the above.

2. In conduction, thermal energy is transported by

a the movement of a fluid.

b the collisions of atoms.

c electromagnetic fields.

d the propagation of sound waves.

3. An object has a KE of 7 J, a GPE of 24 J and a spring PE of 10 J. What is the ME of the object?

a 31 J

b 41 J

c 17 J

d 12 J

e. none of the above.

 4. An object has a velocity toward the east. If a force directed toward the east acts on the object, it will cause the kinetic energy of the object to _______ .

a increase

b decrease

c remain the same

d We can’t say.

5. Consider the human body to be a heat engine with an efficiency of 20%. This means that

a only 20% of the food you eat is digested.

b 80% of the energy you obtain from food is destroyed.

c you should spend 80% of each day lying quietly without working.

d only 20% of the energy you obtain from food can be used to do work.

e. none of the above.

 6. Which has the greater momentum, a moving bullet or the gun from which it came?

a Cannot tell from the information given.

b the Gun, since it has more mass

c the Bullet, since it has a higher speed

d They have equal and opposite momentum.

 7. Who is given credit for discovering that heat is NOT a fluid as was commonly believed?

a Aristotle

b Joule

c Carnot

d Count Rumford

 8. Under what condition is the total linear momentum of a system conserved?

a It is always conserved.

b When there is no net outside force.

c When there is no net external torque.

d When the kinetic energy is also conserved.

e. none of the above.

9. Assume that two cars have the same mass, but that the red car has one third the speed of the blue car. We then know that the red car has ______ the kinetic energy as the blue car.

a one ninth as much

b one third as much

c three times as much

d nine times as much

e. none of the above.

10. In physics, work is defined as the product of the

a net force and the distance traveled.

b net force parallel to the motion and the distance traveled.

c net force parallel to the motion and the time it is applied.

d applied force and the distance traveled.

11. An Impulse of 50 kg m/s is given to an object. If the impulse only lasted for 0.5 seconds, what average force was applied to the object?

a 100 kg m/s²

b 0.002 kg m/s

c 125 kg Newtons

d 250 impulse units
e. none of the above.

12. A ball on the end of a string travels in a horizontal circle at a constant speed. The circle has a circumference of 3 m, the ball has a speed of 2 m/s and the centripetal force is 4 N. How much work is done on the ball each time it goes around?

a zero since force is perpendicular to the motion

b 6 J

c 38 J

d 4800 J

e. none of the above.

13. An object moving at 10 m/s has a KE of 350 J. What is the object’s mass?

a 10 m/s

b 35 kg

c 70 kg

d 7 kg

e. none of the above.

14. A ball dropped from a height of 10 m only bounces to a height of 5 m. Which of the following statements is valid for this situation?

a Kinetic energy is conserved.

b Mechanical energy is conserved.

c Gravitational potential energy is conserved.

d None of the above.

15. The third law of thermodynamics

a is a restatement of the law of conservation of energy.

b says that heat cannot be completely converted to mechanical energy.

c says that we can never reach the absolute zero of temperature.

d says that small objects contain less heat than large objects.

16. If a system has no change in internal energy, we can say that

a the system lost no heat.

b no work was done on the system.

c the amount of work done by the system was equal and opposite to the heat gained.

d the change in heat energy produced a temperature change.

17. Which of the following statements does NOT correctly describe what happens when a cool block is placed in contact with a hot block?

a Heat flows from the hot block to the cool block.

b The average kinetic energy of the particles decreases in the hot block and increases in the cool block.

c The temperature of the hot block decreases and that of the cool block increases.

d Temperature flows from the hot block to the cool block.

18. Two objects are in thermal equilibrium if

a they have the same temperature.

b they are each in thermal equilibrium with a third object

c they are in thermal contact and there is no net flow of thermal energy.

d any of the above is true.

COMPLETION QUESTIONS: Complete the following with the best word or words. 2 points per blank.

19. ___________________ is due to the noncollective motion of atoms / molecules.

20. The change in entropy of the universe is zero only for __________________.

21. The work done by friction is always ________________________________ .

22. The bathroom floor feels cold to our bare feet because the floor is a thermal _________.

23. ___________ is the mechanism of heat transfer that can transport energy through a vacuum.

24. Newton’s second law can be rearranged to show that the _____________ is equal to the change in the __________________ .

QUESTIONS

1. Discuss the demonstration that made use of the rotating stool and the two 2 kg masses.

2. Discuss how the concept of entropy connects the microscopic and macroscopic (everyday) worlds.

 3. a) Briefly discuss the work-energy theorem.

         b) What is meant by the ‘quality’ of energy? You may wish to give examples to support your statements.

4. Sketch the schematic representations of the indicated devices indicating reservoirs, and showing the direction and relative quantity of heat flow. (8 pts)

a) Refrigerator b) Heat engine

5. You are lowered into the center of a frozen, totally frictionless pond, how can you get to the safety of the edge? It is so slick that you cannot stand up. Any attempt to do so causes you to fall.

 6. State the Second Law of Thermodynamics in all 3 contexts used in class.

7. Why is mechanical energy not conserved if friction is present? Is energy conserved when friction is present?