Question 1

A 70.0 kg running back is moving north at 5.00 m/s and collides with an 80.0 kg linebacker moving west at 4.00 m/s. After they stick together, what is the magnitude of their velocity immediately after the collision?

Accepted Answer

$$2.98\ \mathrm{m/s}$$

Question 2

A 4.00 kg bomb at rest explodes into three pieces. Piece 1 (1.00 kg) flies north at 20.0 m/s, Piece 2 (1.50 kg) flies east at 16.0 m/s. What is the magnitude of the velocity of Piece 3 immediately after the explosion?

Accepted Answer

$$12.8\ \mathrm{m/s}$$

Question 3

A block slides from rest down a frictionless ramp and then across a rough horizontal surface until it stops. According to the work-energy theorem, which of the following is true?

Accepted Answer

The net work done on the block equals its change in kinetic energy.

Question 4

A 0.300 kg block is dropped from 0.800 m onto a spring with $$k = 500\ \mathrm{N/m}. $$What is the maximum compression $$x of $$the spring?

Accepted Answer

$$0.154\ \mathrm{m}$$

Question 5

A bullet of mass $$8.00\ \mathrm{g}$$ traveling at $$350\ \mathrm{m/s}$$ embeds in a $$2.00\ \mathrm{kg}$$ block at rest on a $$1.50\ \mathrm{m}$$ high table. What is the speed of the block and bullet immediately after the collision?

Accepted Answer

$$1.39\ \mathrm{m/s}$$

Question 6

A spring is stretched by a distance $$x$$ and has potential energy $$U. If it is $$stretched by $$3x$$, what is the new potential energy?

Accepted Answer

$$9U$$

Question 7

A monatomic ideal gas ($$C_v = \frac{3R}{2}$$ per mole) undergoes an isochoric heating from $$T_1 = 300$$\ \mathrm{K}$$, p_1$ = 1.00 	imes 10^5$\ \mathrm{Pa}$$, $$V = 0.0200\ \mathrm{m}^3 to$$ $$p_2 = 3.00$$ 	imes $$10^5$$\ \mathrm{Pa}$$. What is the final temperature after this step?

Accepted Answer

$$900\ \mathrm{K}$$

Question 8

A 0.500 kg copper block at $$200\ ^\circ\mathrm{C} is $$dropped into $$2.00\ \mathrm{kg} of $$water at $$20.0\ ^\circ\mathrm{C} in an $$insulated container. What is the final equilibrium temperature? ($$c_{Cu} = 390\ \mathrm{J/kg\ K}$$, $$c_{water} = 4186\ \mathrm{J/kg\ K})$$

Accepted Answer

$$24.2\ ^\circ\mathrm{C}$$

Question 9

A piston compresses $$0.500$$ mol of ideal gas from $$V_1 = 10.0$$\ \mathrm{L}$$ to V_2$ = 2.50\ \mathrm{L} at $$constant $$T = 350\ \mathrm{K}. $$What is the work done on the gas during this compression?

Accepted Answer

$$2870\ \mathrm{J}$$

Question 10

A heat pump moves heat from a cold to a warm reservoir. Which statement is correct?

Accepted Answer

This process is possible only if external work is done on the system.

Question 11

A block slides from rest down a frictionless ramp onto a rough surface. If the block comes to rest after sliding a distance $$d on $$the rough surface, which equation correctly relates the work done by friction $$W_f to $$the initial potential energy $$U$$?

Accepted Answer

$$W_f = U$$

Question 12

A 1 kg object moving at $$2\ \mathrm{m/s}$$ has momentum $$p_1. A 2 kg $$object moving at $$1\ \mathrm{m/s}$$ has momentum $$p_2. $$Which is correct?

Accepted Answer

$$p_1$$ = $$p_2$$

Question 13

A monatomic ideal gas undergoes a cyclic process. Which of the following is true about the net work done by the gas over one complete cycle?

Accepted Answer

It is equal to the net heat absorbed by the gas.

Question 14

A block slides from rest down a frictionless ramp and compresses a spring at the bottom. If the block is released from height $$h$$ and the spring constant is $$k$$, what is the maximum compression $$x_{max} of $$the spring?

Accepted Answer

$$x_{max} = \sqrt{\frac{2mgh}{k}}$$

Question 15

A 0.200 kg sample of ice at $$-20.0\ ^\circ\mathrm{C} is $$converted to steam at $$130\ ^\circ\mathrm{C}. $$Which stage requires the most energy?

Accepted Answer

Boiling the water at $$100\ ^\circ\mathrm{C}$$

Question 16

A roller coaster car of mass $$850\ \mathrm{kg}$$ starts from rest at $$h = 30.0\ \mathrm{m} on a $$frictionless track with a loop of radius $$R = 7.50\ \mathrm{m} ($$bottom at ground). What is the speed at the top of the loop?

Accepted Answer

$$20.4\ \mathrm{m/s}$$

Question 17

An ideal gas at constant temperature has its pressure doubled. What happens to its volume?

Accepted Answer

It is halved

Question 18

Which best explains why the root-mean-square (rms) speed of gas molecules increases with temperature?

Accepted Answer

Temperature is a direct measure of average molecular kinetic energy

Question 19

A block slides from rest down a frictionless ramp onto a rough surface. If the block comes to rest after sliding a distance $$d on $$the rough surface, which equation correctly relates the work done by friction $$W_f to $$the initial potential energy $$U$$?

Accepted Answer

$$W_f = U$$

Physics 2010 Exam 3 Practice Guidance: Momentum, Energy & Thermodynamics

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