A2L Item 139

Goal: Reasoning with work

Source: UMPERG-ctqpe50

In which case would you do the least amount of work?

  1. You push a box 10 m across a floor.
  2. You pick up the box, walk 10 m and put the box down on the floor.
  3. You pick up the box, walk 10 m and drop the box.
  4. Both 2 and 3
  5. Work done is the same in all cases.
  6. Cannot be determined from info given.



(6) This problem is intended to elicit a vigorous discussion of
work. Students have a difficult time reconciling the formal definition
of work with the colloquial one. Every one of the answers is defensible
depending upon one’s perspective. Lifting a heavy box requires doing
work against gravity. Putting it down actually requires that you do the
same amount of work. Gravity does no net work, but humans are not
conservative systems. Depending upon the surface it may be more
advantageous to push the box.