Question

1. A gallon of water is receiving 100 J of latent heat. In that process its temperature

a. increases

b. decreases

c. remains constant

2. A 100 kg rock is at rest. It is then dropped and falls through a height of 20 m. How fast is it approximately
moving after dropping that distance?

a. 10 m/s

b. 15 m/s

c. 20 m.s

d. 25 m/s

e. None of the above

3. Of the following processes, which one involves the most energy transfer? (Useful constants: specific heat of ice:
2100 J/(kgC), specific heat of water: 4190 J/(kgC), heat of fusion: 334x10³ J/kg, heat of vaporization:
2.26x10⁶ J/kg).

a. change the temperature of 100 kg of ice at -10 degrees C to the freezing point.

b. convert 100 kg of ice at 0 degrees C into water at at 0 degrees C.

c. change the temperature of 100 kg of water at 0 degrees C to the boiling point.

d. convert 100 kg of water at 100C into steam at 100 degrees C.

4. Which best describes the relationship between two systems in thermal equilibrium?

a. no net energy is exchanged

b. constant heat ow

c. masses are equal

d. zero velocity

5. A wrench is used to loosen a nut such that its moment arm is 10 cm and the applied force is 20 N. The torque produced is

a. 1 Nm

b. 2 Nm

c. 20 Nm

d. 200 Nm

Answer 1

1. C. Remains constant

Because during the latent heat process only phase change occurs temperature remains constant.

2.c. 20 m/s

Here we have given mass of the rock is 100kg

Height of the rock is 20m

So that using energy conservation principles we have

PE = KE

Mgh = 0.5 mV^2

V = (9.8*20×2)^0.5 = 20 m/s

3.c. change the temperature of 100 kg of water at 0 degrees C to the boiling point.

The processes, which one involves the most energy transfer will be ,have the higher temperature difference and for this case only option c satisfies.

4.a. no net energy is exchanged

Because in this case no heat transfer between bodies and all of the participating bodies are at the same temperature.

5. b.) 2Nm

Here we have given that,

moment arm is 10 cm and the applied force is 20 N

Then the torque produced is = F×r = 20 ×0.1 = 2 Nm