Question

the thermal energy of a system increases by 400 j, and 1100 j of heat is added to the system.
how much work did the system do?
400 j
700 j
1100 j
1500 j

Explanation:

Step1: Recall first law of thermodynamics

The first law is $\Delta U = Q - W$, where $\Delta U$ is the change in internal (thermal) energy, $Q$ is heat added to the system, and $W$ is work done by the system.

Step2: Rearrange to solve for $W$

Rearrange the formula to isolate work: $W = Q - \Delta U$

Step3: Substitute given values

Substitute $Q=1100\ \text{J}$ and $\Delta U=400\ \text{J}$:
$W = 1100 - 400$

Answer:

B. 700 J