7. A stock person at the local grocery store has the job of 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, and 5) lowering the boxes slowly to the floor. During which of the five segments of the stock person's task is positive work being done on the boxes?
A. 1) and 5),
B. 1),
C. 1), 2), 4), and 5),
D. 1) and 2),
E. 2) and 3).
C. 1), 2), 4), and 5).
To determine during which segments of the stock person's task positive work is being done on the boxes, we need to understand the concept of work.
Work is defined as the product of the applied force on an object and the displacement of the object in the direction of the force. In this case, positive work is done when the force applied on the boxes is in the same direction as the displacement of the boxes.
Let's analyze each segment of the task:
1) Picking up boxes from the stockroom floor: Positive work is done here because the force applied by the stock person is in the same direction as the displacement of the boxes.
2) Accelerating to a comfortable speed: No work is done here because there is no displacement in the direction of the applied force. The force here is applied to the stock person, not the boxes.
3) Carrying the boxes to the tomato display at constant speed: No work is done here because there is no change in the displacement of the boxes. The applied force and the displacement are perpendicular.
4) Decelerating to a stop: Positive work is done here because the force applied by the stock person is in the opposite direction of the displacement of the boxes. This is known as negative work.
5) Lowering the boxes slowly to the floor: Positive work is done here because the force applied by the stock person is in the same direction as the displacement of the boxes.
Based on this analysis, the answer is:
C. 1), 2), 4), and 5)
Positive work is being done on an object when the force applied to the object and the displacement of the object are in the same direction.
In this case, the stock person is applying a force to the boxes to pick them up, accelerate them, carry them, decelerate them, and lower them.
So, positive work is being done on the boxes during segments 1) and 5) when the stock person is picking up the boxes from the stockroom floor and lowering them to the floor.
Therefore, the correct answer is option A) 1) and 5).