Question

in which case is work being done? birdwatching on a bench; reading in a chair; pushing a sandbag; listening to music

Explanation:

To determine when work is done, we use the physics definition: work is done when a force causes displacement ($W = Fd\cos\theta$, where $F$ is force, $d$ is displacement, and $\theta$ is the angle between them).

• Birdwatching on a bench: No force causing displacement (stationary).
• Reading in a chair: No force causing displacement (stationary).
• Pushing a sandbag: A force is applied, and if the sandbag moves, displacement occurs (so work is done).
• Listening to music: No force causing displacement (stationary).

Answer:

pushing a sandbag