Work: A stock person at the local grocery store has a job consisting of the following five segments: (1) picking up boxes of tomatoes from the stockroom floor
(2) accelerating to a comfortable speed
(3) carrying the boxes to the tomato display at constant speed
(4) decelerating to a stop
(5) lowering the boxes slowly to the floor.
During which of the five segments of the job does the stock person do positive work on the boxes?

Question

Quizplus · Accepted Answer

Positive work is done when the force applied to an object has a component in the direction of the object's displacement. In segment (1), lifting the boxes off the floor involves applying a force upward, which is in the direction of the displacement, thus doing positive work. In segment (2), accelerating the boxes to a comfortable speed also involves applying a force in the direction of the boxes' motion, again doing positive work. Segments (3), (4), and (5) involve either no work in the case of constant speed (since no force is needed to maintain speed in an ideal scenario without friction) or work that does not contribute to the boxes' displacement in the desired direction (decelerating and lowering the boxes do not involve applying a force in the direction of the boxes' initial displacement).

Work: a Stock Person at the Local Grocery Store Has