Question

A. What is the change in internal energy for each of the following situations? q = 7.9 J out of the system and w = 3.6 J done on the system q = 1.5 J into the system and w = 7.5 J done on the system

Answer 1

Answer: $-4.3\ J,\ 9\ J$

Explanation:

Given

(a)

Heat transfer $Q=-7.9\ J\quad \text{taken}$

Work done $W=-3.6\ J\quad \text{on the system}$

Change in the internal kinetic energy is

$\Delta U=Q-W\\\Rightarrow \Delta U=-7.9-(-3.6)\\\Rightarrow \Delta U=-4.3\ J$

(b)

Heat transfer $Q=1.5\ J\quad \text{given}$

Work done $W=-7.5\ J\quad \text{on the system}$

Change in the internal kinetic energy is

$\Delta U=Q-W\\\Rightarrow \Delta U=1.5-(-7.5)\\\Rightarrow \Delta U=9\ J$