PHYSICS 313

Problem set 2 2001

Given September 17

Due September 24

Problem 1:

A waterfall is 100 m high.

a)

Assuming that all the potential energy lost by the falling water is used to warm the water. By how much will the temperature rise?

b)

Assume instead that the potential energy lost by the water is used to vaporize some of the water. What fraction of the water will vaporize? (Assume the latent heat of evaporation is the same as at 100 ^oC, namely 540 kcal kg^-1)

Problem 2:

Which of the following statements is most likely to be correct? The heat capacity of a 0.4 kg chunk of copper at room temperature is

a) 1.5 J K ^–1? b) 15 J K ^–1? c) 150 J K ^–1?

The atomic weight of copper is 63.54 g mol^-1.

Problem 3:

A mol of an ideal gas is initially at pressure P, Volume V. It is then compressed adiabatically until its pressure is 2P. It is next expanded under constant pressure until the volume again is V. It is finally cooled at constant volume until the pressure again is P. Assume that g=1.4.

a)

Calculate the temperature at each step of the cycle.

b)

What is the heat Q and work W at each step of the cycle. Assume the sign convention

DU=Q+W.

c)

What is the total work and heat done on the gas during the cycle.