1. PAL 3/9/12
For each of the following systems, use CONSERVATION OF ENERGY to explain what is happening to the system. Justify all answers.
Consider a system consisting of air inside a piston of a diesel engine. The air is initially in equilibrium with the ambient air temperature. Then the air is compressed, so it ends up at a higher temperature than it started at. The piston is not insulated.
Does the system gain or lose (or neither) energy due to work?
Does the system gain or lose (or neither) energy due to heat?
Does the internal energy of the system increase or decrease or remain the same?
Which is greater: the magnitude of the work or the magnitude of the heat, or are they equal?

2. Consider a system consisting of air inside a syringe
Consider a system consisting of air inside a syringe. The air is initially compressed and in thermal equilibrium with the room temperature. Then the air is allowed to expand very slowly, so that it remains always at room temperature.
Does the system gain or lose (or neither) energy due to work?
Does the system gain or lose (or neither) energy due to heat?
Does the internal energy of the system increase or decrease or remain the same?
Which is greater: the magnitude of the work or the magnitude of the heat, or are they equal? 2

3. Consider a system consisting of two ice cubes
Consider a system consisting of two ice cubes. You are outside on a day when the air temperature is 32oF (0oC). You are holding the ice cubes with very well-insulated gloves. You rub the ice cubes together until they begin to melt.
Does the system gain or lose (or neither) energy due to work?
Does the system gain or lose (or neither) energy due to heat?
Is the final temperature greater than, equal to, or the same as the initial temperature?
Does the internal energy of the system increase or decrease or remain the same?
Which is greater: the magnitude of the work or the magnitude of the heat, or are they equal? 3

4. Consider a system consisting of a ball held at rest on the moon
Consider a system consisting of a ball held at rest on the moon. The ball is released and begins to fall. (Consider the final time to be as it is falling, before it hits the ground.)
Does the system gain or lose (or neither) energy due to work?
Does the system gain or lose (or neither) energy due to heat?
Is the final temperature greater than, equal to, or the same as the initial temperature?
Does the internal energy of the system increase or decrease or remain the same?
Explain how energy is conserved in this case. 4