Q: A diver descends to a depth of $$20\ \mathrm{m} in $$seawater ($$\rho = 1025\ \mathrm{kg/m}^3). $$What is the gauge pressure at this depth? (Use $$g = 9.8\ \mathrm{m/s}^2)$$

$$2.0 \times 10^5$\ \mathrm{Pa}$$

Q: A piston contains $$0.5\ \mathrm{mol} of an $$ideal gas at $$400\ \mathrm{K}. $$What is the average kinetic energy per molecule? (Use $$k_B = 1.38 \times 10$$^{-23}$$\ \mathrm{J/K})$$

$$8.28 \times 10$$^{-21}$$\ \mathrm{J}$$

Question 1

A hydraulic lift is used to raise a car weighing $$12,000\ \mathrm{N}. If $$the area of the input piston is $$0.01\ \mathrm{m}^2$$ and the area of the output piston is $$0.5\ \mathrm{m}^2$$, what is the minimum force that must be applied to the input piston to lift the car? (Neglect friction and assume the fluid is incompressible.)

Accepted Answer

$$240\ \mathrm{N}$$

Question 2

Which of the following best explains why gases are compressible while liquids are not?

Accepted Answer

Gases have much greater intermolecular distances than liquids, allowing their volume to decrease significantly under pressure.

Question 3

A cube of wood with density $$600\ \mathrm{kg/m}^3$$ and volume $$0.02\ \mathrm{m}^3$$ floats in water (density $$1000\ \mathrm{kg/m}^3). $$What volume of the cube is submerged?

Accepted Answer

$$0.012\ \mathrm{m}^3$$

Question 4

Which of the following statements about pressure in fluids is correct?

Accepted Answer

Pressure at a point in a fluid at rest depends only on the depth and the density of the fluid, not on the shape of the container.

Question 5

A gas is compressed isothermally from $$4.0\ \mathrm{L} to$$ $$2.0\ \mathrm{L} at a $$constant temperature of $$300\ \mathrm{K}. If $$the initial pressure is $$100\ \mathrm{kPa}$$, what is the final pressure?

Accepted Answer

$$200\ \mathrm{kPa}$$

Question 6

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

Accepted Answer

The entropy of an isolated system never decreases; it either increases or remains constant.

Question 7

A heat engine absorbs $$500\ \mathrm{J} of $$heat from a hot reservoir and expels $$300\ \mathrm{J} to a $$cold reservoir in each cycle. What is the efficiency of the engine?

Accepted Answer

$$0.4$$

Question 8

Which of the following is a correct application of Pascal's Principle?

Accepted Answer

A small force applied to a small piston in a hydraulic lift results in a larger force on a larger piston.

Question 9

A sample of ideal gas is held at constant volume. If the temperature is doubled, what happens to the pressure?

Accepted Answer

It doubles.

Question 10

Which of the following is the correct expression for the buoyant force $$F_b$$ acting on an object submerged in a fluid?

Accepted Answer

$$F_b = \rho_{fluid} V_{displaced} g$$

Question 11

A Carnot engine operates between a hot reservoir at $$600\ \mathrm{K}$$ and a cold reservoir at $$300\ \mathrm{K}. $$What is the maximum possible efficiency?

Accepted Answer

$$0.5$$

Question 12

Which of the following scenarios best illustrates an increase in entropy?

Accepted Answer

An ice cube melting in a glass of warm water.

Question 13

A sealed container holds $$2.0\ \mathrm{mol} of an $$ideal gas at $$300\ \mathrm{K}$$ and $$100\ \mathrm{kPa}. $$What is the volume of the container? (Use $$R = 8.31\ \mathrm{J/(mol\cdot K)})$$

Accepted Answer

$$0.498\ \mathrm{m}^3$$

Question 14

Which of the following is NOT an assumption of the ideal gas law?

Accepted Answer

Gas molecules experience significant intermolecular forces.

Question 15

A diver descends to a depth of $$20\ \mathrm{m} in $$seawater ($$\rho = 1025\ \mathrm{kg/m}^3). $$What is the gauge pressure at this depth? (Use $$g = 9.8\ \mathrm{m/s}^2)$$

Accepted Answer

$$2.0 	imes 10^5$\ \mathrm{Pa}$$

Question 16

Which of the following best describes the physical meaning of temperature in thermal physics?

Accepted Answer

It is a measure of the average kinetic energy of the particles in a system.

Question 17

A piston contains $$0.5\ \mathrm{mol} of an $$ideal gas at $$400\ \mathrm{K}. $$What is the average kinetic energy per molecule? (Use $$k_B = 1.38 	imes 10$$^{-23}$$\ \mathrm{J/K})$$

Accepted Answer

$$8.28 	imes 10$$^{-21}$$\ \mathrm{J}$$

Question 18

Which of the following is the correct expression for the work done by a gas during an isobaric expansion from volume $$V_1 to$$ $$V_2 at $$pressure $$P$$?

Accepted Answer

$$W = P (V_2$ - V_1$)$$

Question 19

A refrigerator removes $$1200\ \mathrm{J} of $$heat from its interior and expels $$1600\ \mathrm{J} to $$the kitchen. What is the work input required?

Accepted Answer

$$400\ \mathrm{J}$$

Question 20

Which of the following best describes why a steel ship floats on water?

Accepted Answer

The average density of the ship (including the air inside) is less than the density of water.

Fluids and Thermal Physics: Study Guide for Physics 201

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