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?
A) (1) and (5)
B) (1) only
C) (1), (2), (4), and (5)
D) (1) and (2)
E) (2) and (3)

Question

Quizplus · Accepted Answer

Positive work is done when the force applied to an object is 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 boxes' displacement, thus doing positive work. In segment (2), accelerating to a comfortable speed also involves applying a force in the direction of the boxes' motion, doing positive work. Segments (3), (4), and (5) involve either no work in the case of constant speed (since there's no acceleration) or work that does not contribute to the boxes' displacement in the desired direction, such as decelerating or lowering the boxes.

A Stock Person at the Local Grocery Store Has a Job