which situations show examples of work occurring? check all that apply. a student carries a stack of books…
which situations show examples of work occurring? check all that apply. a student carries a stack of books to the library. a shopping cart is pushed through a parking lot. a hockey puck slides on ice, with constant velocity. an airplane slows to a stop on a runway. a pool ball bounces off the edge of a pool table.
Answer
Answer:
- A shopping cart is pushed through a parking lot.
- An airplane slows to a stop on a runway.
Explanation:
Step1: Recall work - energy theorem
Work is done when a force causes a displacement in the direction of the force, $W = F\cdot d\cdot\cos\theta$ where $\theta$ is the angle between force $F$ and displacement $d$.
Step2: Analyze each situation
- For a student carrying books to the library, the force is vertical (against gravity) and displacement is horizontal, $\theta = 90^{\circ}$, $\cos\theta=0$, so $W = 0$.
- For a shopping cart pushed through a parking lot, a force is applied in the direction of displacement, work is done.
- For a hockey puck sliding with constant velocity, no net - force acts in the direction of motion (assuming no friction), so work done is zero.
- For an airplane slowing to a stop, a force (e.g., friction, air - resistance) acts in the opposite direction of motion, work is done.
- For a pool ball bouncing off the edge of a pool table, the force is perpendicular to the direction of motion during the bounce at the instant of contact, $\theta = 90^{\circ}$, $\cos\theta = 0$, so work done is zero.