Why is work said to be done when a student lifts a heavy box from the floor to a table, but NOT when holding…

Why is work said to be done when a student lifts a heavy box from the floor to a table, but NOT when holding the same box stationary at table height?
  1. Lifting requires energy, but holding stationary does not require any energy
  2. Force causes displacement during lifting, whereas displacement is zero while holding it stationary
  3. Gravity acts on the box only while it is being lifted
  4. The mass of the box decreases once it reaches the table height

Solution

In science, work requires both force and displacement in the direction of force. Holding the box stationary involves zero displacement, so no scientific work is done.

Asked in: Homi Bhabha Practice

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