Q: A 2 kg block is pushed 5 meters along a frictionless surface by a constant force of 10 N applied at an angle of 60° to the direction of motion. How much work is done by the force on the block?

$$W = 10 \times 5 \times \cos 60^\circ = 25\ \mathrm{J}$$

Q: A 1.5 kg mass slides down a 1-meter-high frictionless incline starting from rest. What is its speed at the bottom?

$$v = \sqrt{2gh} = \sqrt{2 \times 9.8 \times 1} = 4.43\ \mathrm{m/s}$$

Q: A gas in a piston expands from 2 L to 6 L at a constant pressure of 100 kPa. What is the work done by the gas?

$$W = P \Delta V = 100{,}000 \times (0.006 - 0.002) = 400\ \mathrm{J}$$

Q: A copper rod of length 2 m is heated from 20°C to 100°C. If the coefficient of linear expansion for copper is $$16 \times 10$$^{-6}$$\ \mathrm{C}^{-1}$$, what is the change in length?

$$\Delta L = \alpha L_0$ \Delta T = 16 \times 10$$^{-6}$$ \times 2 \times 80 = 0.00256\ \mathrm{m}$$

Q: A 0.5 kg block of ice at 0°C is placed in 100 g of water at 20°C. If the latent heat of fusion for ice is $$334{,}000\ \mathrm{J/kg}$$ and the specific heat of water is $$4{,}186\ \mathrm{J/(kg\cdot K)}$$, how much heat is required to melt all the ice?

$$Q = mL = 0.5 \times 334{,}000 = 167{,}000\ \mathrm{J}$$

Question 1

A 2 kg block is pushed 5 meters along a frictionless surface by a constant force of 10 N applied at an angle of 60° to the direction of motion. How much work is done by the force on the block?

Accepted Answer

$$W = 10 	imes 5 	imes \cos 60^\circ = 25\ \mathrm{J}$$

Question 2

Which of the following statements about conservative forces is correct?

Accepted Answer

The work done by a conservative force depends only on the initial and final positions, not on the path taken.

Question 3

A 1.5 kg mass slides down a 1-meter-high frictionless incline starting from rest. What is its speed at the bottom?

Accepted Answer

$$v = \sqrt{2gh} = \sqrt{2 	imes 9.8 	imes 1} = 4.43\ \mathrm{m/s}$$

Question 4

Which of the following best describes the physical meaning of temperature?

Accepted Answer

Temperature is related to the average kinetic energy of atoms and molecules in a material.

Question 5

A gas in a piston expands from 2 L to 6 L at a constant pressure of 100 kPa. What is the work done by the gas?

Accepted Answer

$$W = P \Delta V = 100{,}000 	imes (0.006 - 0.002) = 400\ \mathrm{J}$$

Question 6

Which law of thermodynamics states that the entropy of the universe always increases?

Accepted Answer

The Second Law of Thermodynamics

Question 7

A copper rod of length 2 m is heated from 20°C to 100°C. If the coefficient of linear expansion for copper is $$16 	imes 10$$^{-6}$$\ \mathrm{C}^{-1}$$, what is the change in length?

Accepted Answer

$$\Delta L = \alpha L_0$ \Delta T = 16 	imes 10$$^{-6}$$ 	imes 2 	imes 80 = 0.00256\ \mathrm{m}$$

Question 8

Which equation correctly expresses the Stefan-Boltzmann Law for the power radiated by a blackbody?

Accepted Answer

$$P = \epsilon \sigma A T^4$

Question 9

A 0.5 kg block of ice at 0°C is placed in 100 g of water at 20°C. If the latent heat of fusion for ice is $$334{,}000\ \mathrm{J/kg}$$ and the specific heat of water is $$4{,}186\ \mathrm{J/(kg\cdot K)}$$, how much heat is required to melt all the ice?

Accepted Answer

$$Q = mL = 0.5 	imes 334{,}000 = 167{,}000\ \mathrm{J}$$

Question 10

Which of the following is the correct form of the ideal gas law for $$n$$ moles of gas?

Accepted Answer

$$PV = nRT$$

Question 11

A heat engine absorbs 500 J of heat from a hot reservoir and expels 300 J to a cold reservoir. How much work does it do?

Accepted Answer

$$W = Q_{in} - Q_{out} = 500 - 300 = 200\ \mathrm{J}$$

Question 12

Which of the following best describes the Zeroth Law of Thermodynamics?

Accepted Answer

If two systems are each in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.

Question 13

A 3.0 kg object is moving at 4.0 m/s. What is its kinetic energy?

Accepted Answer

$$KE = \frac{1}{2}mv^2$ = \frac{1}{2} 	imes 3.0 	imes 16 = 24\ \mathrm{J}$$

Question 14

Which of the following is NOT a correct statement about heat engines?

Accepted Answer

Heat engines convert all absorbed heat into work.

Question 15

If the pressure of an ideal gas is kept constant and the temperature is doubled, what happens to the volume?

Accepted Answer

The volume doubles.

Question 16

Which equation gives the internal energy of a monatomic ideal gas containing $$N$$ particles?

Accepted Answer

$$U = \frac{3}{2}NkT$$

Question 17

A metal rod of length $$L is $$heated so its temperature increases by $$\Delta T. $$Which equation gives the change in length?

Accepted Answer

$$\Delta L = \alpha L \Delta T$$

Question 18

Which of the following best describes the physical meaning of the area under a $$P$$-$$V$$ curve for a gas?

Accepted Answer

It represents the work done by or on the gas.

Question 19

Which equation describes the heat $$Q$$ transferred by conduction through a material of cross-sectional area $$A$$, thickness $$L$$, and thermal conductivity $$k$$ over time $$t$$ with temperature difference $$\Delta T$$?

Accepted Answer

$$Q = kA \left( \frac{\Delta T}{L} \right) t$$

Work, Kinetic Energy, and Thermodynamics: PHYS 111 Study Notes

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