sample exam 3
Student: ___________________________________________________________________________
1. On a cold winter's morning you awake and step out of bed. One foot is on the tile floor and the other is on a rug on the floor. Which statement is true? 
 
A. The tile feels colder because it is smoother than the rug.
B. The tile feels colder because it conducts heat more rapidly away from your foot.
C. The tile feels colder because it is connected to the cold ground outside.
D. The tile feels colder because it cannot absorb water like the rug can.
 
2. Objects A and B are at the same temperature. Object A now has its temperature increased by one Fahrenheit degree, while B has its temperature increased by one Kelvin degree. Which object now has higher temperature? 
 
A. Object A.
B. Object B.
C. Both have the same temperature.
D. Impossible to tell from this data.
 
3. A box of graham crackers is labeled "120 Calories per serving". Assuming this means 120 kcal, the energy of a serving of the graham crackers is about 
 
A. 120 J.
B. 4.2 103 J.
C. 5 104 J.
D. 5 105 J.
 
4. Which of the following temperatures is the lowest? 
 
A. 0oC
B. 0oF
C. 263 K
D. All are the same.
 
5. Four samples of steel, lead, alcohol and glass all have the same mass and are all initially at 20oC. After 100 calories of heat is added to each sample, the final temperatures are 38.2oC for the steel, 85.6oC for the lead, 23.4oC for the alcohol, and 30oC for the glass. Which of these four materials has the largest specific heat capacity? 
 
A. The steel.
B. The lead.
C. The alcohol.
D. The glass.
E. All have same heat capacity, since all absorbed 100 cal of heat.
 
6. The term heat in physics is 
 
A. equivalent to temperature.
B. equivalent to internal energy.
C. any energy transferred to a body that raises the temperature of the body.
D. energy transferred to a body because of a difference in temperature.
E. the same as work.
 
7. Heat flows into a gas in a piston and the gas performs some work on its surroundings. The amount of work done is less than the heat added. In this situation, 
 
A. the internal energy of the gas decreased.
B. the internal energy of the gas did not change.
C. the internal energy of the gas increased.
D. the gas experienced a phase change.
E. energy is not conserved and so it cannot happen.
 
8. Hot cider is poured into a metal cup. Shortly thereafter the handle of the cup becomes hot. This is due to the process of 
 
A. conduction.
B. convection.
C. radiation.
D. osmosis.
 
9. Which of the following units is not an energy unit? 
 
A. Calorie.
B. Joule.
C. Kilowatt-hour.
D. Horsepower.
E. Kilocalorie.
 
10. If you stand near a large fire, your face will be cooler if you place your hand between your face and the fire. Your hand is preventing heat flow by 
 
A. conduction.
B. convection.
C. radiation.
D. latent heat.
 
11. Whenever a gas is compressed, 
 
A. work must be done on the gas.
B. its internal energy must get smaller.
C. heat must leave the gas.
D. the temperature of the gas must get smaller.
 
12. Energy added to a cyclical heat engine 
 
A. is completely converted to external work.
B. is converted to increased internal energy in the engine plus external work.
C. is used to generate work that is greater than the added energy.
D. is converted to work and to waste heat.
 
13. The change in internal energy during one complete cycle of a heat engine 
 
A. equals the net heat flow into the engine.
B. equals zero.
C. equals the heat energy exhausted from the engine.
D. equals the heat energy entering the engine.
 
14. A correct statement of the 2nd Law of Thermodynamics is: 
 
A. the random motion of gas molecules will be decreased if energy is added to a gas.
B. there is no process that can make heat flow from a cold object to a hot object.
C. no heat engine can have an efficiency greater than 30%.
D. heat will not flow spontaneously from a cold object to a hot object.
 
15. The overall direction of change in the universe is toward 
 
A. a state of increased mass in the universe.
B. increased energy content of the universe.
C. a state of greater disorder.
D. a state of increased organization.
 
16. An ideal heat engine is operating between high and low temperature reservoirs. Suppose that now the low temperature reservoir has its temperature lowered, but no other changes are made. This temperature change affects the engine efficiency in the following way: 
 
A. the efficiency increases.
B. the efficiency is unchanged.
C. the efficiency decreases.
D. there is now no way to calculate the efficiency.
 
17. A heat engine having an efficiency of 0.20 takes in 2000 J of energy from the hot reservoir in one cycle. In the same time, how much work will it perform? 
 
A. 0 J
B. 400 J
C. 1000 J
D. 1600 J
E. 10,000 J
 
18. A refrigerator transfers heat from a colder body to a hotter body while energy is used to operate the device. This is 
 
A. allowed only if the internal energy of refrigerator increases.
B. consistent with Clausius's statement of the second law.
C. possible if entropy of the contents of the refrigerator increases.
D. impossible unless the refrigerator uses a Carnot cycle.
 
19. A heat engine that would take in 1000 J of heat from a reservoir at 500 K and exhaust 500 J to a reservoir at 300 K, converting the other 500 J of heat to work, is 
 
A. not thermodynamically possible.
B. possible only for a Carnot cycle.
C. thermodynamically possible.
 
20. If, for an ideal heat engine, QH , QC, and W are, respectively, the heat absorbed, the heat rejected, and the work done per cycle, which of these is true? 
 
A. QH cannot be more than QC.
B. QH cannot be more than W.
C. W cannot be more than QC.
D. QC cannot be more than QH.
 
21. An electron situated near another electron would feel 
 
A. a repulsive electrical force.
B. an attractive electrical force.
C. a repulsive magnetic force.
D. an attractive magnetic force.
E. no forces from the other electron.
 
22. Consider a proton and an electron placed near one another with no other objects close by. They would 
 
A. accelerate away from each other.
B. remain motionless.
C. accelerate toward each other.
D. be pulled together at constant speed.
E. move away from each other at constant speed.
 
23. Two equal positive charges are near each other. If we increase the amount of charge on just one of them, then 
 
A. the larger charge feels a stronger electrical force and the other a weaker electrical force.
B. the electric field points toward the larger charge.
C. the strength of the electric force on both decreases.
D. the electric field at the position of the smaller charge increases.
 
24. An atom has 
 
A. just as many electrons as protons.
B. no neutrons in the nucleus.
C. more protons than electrons.
D. as many electrons as protons and neutrons combined.
E. at least 1 neutron.
 
25. A uniform electric field has a magnitude of 10 N/C and is directed upward. A charge brought into the field experiences a force of 5.0 N downward. The charge must be 
 
A. +50 C.
B. -50 C.
C. +0.5 C.
D. -0.5 C.
E. -2.0 C.
 
26. A charged comb attracts bits of neutral dust in the air. This happens because 
 
A. the dust grounds the comb.
B. the dust becomes charged by induction.
C. the dust becomes polarized.
D. the dust is a good conductor.
 
27. If two metal balls each have a charge of -10-6 C and the repulsive force between them is 1 N, how far apart are they? 
 
A. 9.0 mm
B. 9.4 cm
C. 0.9 m
D. 9.4 m
 
28. Two equal charges repel one another with a force of 4.0  10-4 N when they are 10 cm apart. If they are moved until the separation is 2.5 cm, the repulsive force will be 
 
A. 0.25  10-4N.
B. 1.0  10-4N.
C. 4.0  10-4N.
D. 16  10-4N.
E. 64  10-4N.
 
29. Three equal negative charges are placed at three of the four corners of a square. The direction of the electric field at the remaining corner of the square is 
 
A. along a side of the square toward one of the charges.
B. along a side of the square away from one of the charges.
C. along the diagonal connecting this corner and another charge, away from the other charge.
D. along the diagonal connecting this corner and another charge, toward the other charge.
E. no direction, zero field.
 
30. A uniform electric field has a magnitude of 10 N/C and is directed upward. A charge brought into the field experiences a force of 5.0 N downward. The charge must be 
 
A. +50 C.
B. -50 C.
C. +0.5 C.
D. -0.5 C.
E. -2.0 C.
 
31.  Archimedes' Principle states that  
 
A.  the pressure in a fluid is directly related to the depth below the surface of the fluid. 
B.  an object immersed in a fluid is buoyed up by a force equal to the weight of the displaced fluid. 
C.  the pressure of a fluid is inversely proportional to the temperature of the fluid. 
D.  the velocity of a fluid is directly proportional to the pressure exerted on the fluid. 
 
32. A balloon inflated with helium is able to float toward the ceiling because 
 
A. the weight of the balloon is greater than the weight of the air displaced by the balloon.
B. the balloon and the gas it contains weigh less than the air displaced by the balloon.
C. the density of the gas inside the balloon is greater than the density of the atmosphere.
D. the pressure of the gas inside the balloon is greater than the atmospheric pressure.
E. the pressure of the gas inside the balloon is less than the atmospheric pressure.
 
33. A child is drinking a liquid with a straw. Which of the following statements is true? 
 
A. The fluid is being pulled up into the straw.
B. Longer straws work better because the pressure is larger deeper down.
C. The pressure inside the straw depends on the viscosity of the liquid.
D. The pressure in the straw is reduced and the liquid is pushed upward by atmospheric pressure on the surface of the liquid.
 
34. If you sit in a boat on the edge of a river channel, you might notice the water moving more quickly on the side away from the shore (the channel side). If you are initially moving with the river, you will be pushed 
 
A. into the channel because the water pressure is larger on the shore side.
B. into the channel by the turbulent flow of the water.
C. toward the shore because the water flow is laminar around the boat.
D. toward the shore because the water pressure is smaller on the shore side.
 
35. If the atmospheric pressure is 15 lb/in2 , what is the corresponding downward force on the top of a horizontal square area 6 inches on each side? 
 
A. 540 lbs.
B. 90 lbs.
C. 15 lbs.
D. zero.
 
36. It is observed that as bubbles rise in a deep column of water, the diameter of the bubbles increases. This is best explained by 
 
A. Bernoulli's Principle.
B. Archimedes Principle.
C. Boyle's Law.
D. Pascal's Principle.
 
37. A hydraulic jack is used to lift a load of weight 5000 N. The load-bearing cylinder has a radius of 5 cm, and the other piston has a radius of 1 cm. What force must be exerted on the smaller piston to support the load? 
 
A. 100 N
B. 200 N
C. 1000 N
D. 5000 N
E. 25000 N
 
38. A gas originally occupies a volume of 0.5 m3 at a pressure of 100 kPa. It is slowly allowed to expand until the volume is 2.5 m3. Assuming the temperature is kept constant, the final pressure will be 
 
A. 10 kPa.
B. 20 kPa.
C. 50 kPa.
D. 100 kPa.
E. 500 kPa.
 
39. One section of a pipe carrying water has a cross-sectional area of 20 cm2; in this section the water has flow velocity of 1.0 m/s. Another section of this pipe has a constricted cross-sectional area of 5 cm2. If the flow is steady, what is the water velocity in the constricted section? 
 
A. 0.25 m/s
B. 0.50 m/s
C. 1.0 m/s
D. 2.0 m/s
E. 4.0 m/s
 
40. According to Bernoulli's equation, the pressure in a fluid will tend to decrease if its velocity increases. Assuming that a wind speed of 1 m/s causes a pressure drop of 0.645 Pa, what pressure drop is predicted by Bernoulli's equation for a wind speed of 4 m/s? 
 
A. 10.32 Pa.
B. 2.58 Pa.
C. 1.94 Pa.
D. 1.29 Pa.
.

Answers 

1.b
2.b
3.d
4.b
5.c
6.d
7.c
8.a
9.d
10.c
11.a
12.d
13.b
14.d
15.c
16.a
17.b
18.b
19.a
20.d
21.a
22.c
23.d
24.a
25.d
26.c
27.b
28.e
29.d
30.d
31.b
32.b
33.d
34.a
35.a
36.c
37.b
38.b
39.e
40.a

1. COP = 11.9
2. 0.001J, 0.50V,-0.001J
3. 1225Pa, 90.085m/s 		4.  2.4 ohms, 50A, 6000W

1.	A Carnot refrigerator operates at 2.2 degrees Celsius and 25.2 degrees Celsius.  Calculate the COP.
2.	A 0.002C charge moves 0.2m in an electric field of -25N/C.  Calculate the change in potential energy, the change in voltage and the work done on the charge.
3.	The total area of an airplane’s wings is 40.0mand its weight is 49.0KN.  The density of air is 1.3kg/m.  Calculate the difference in air pressure over its wings.   If the speed of air is 100m/s over the top surface, calculate the speed over the bottom surface.
4.	4 resistors, 5, 10, 15, and 20 ohms are connected in parallel to a 120 volt supply.  Calculate the total resistance, total current, and power output.