Question

Which of the following does not involve work? 1. A child is pushed on a swing. 2. A golf ball is struck. 3. A weight lifter does military presses (lifting weights over his head.) 4. A professor picks up a piece of chalk from the floor. 5. A runner stretches by pushing against a wall.

Answer 1

From the work theorem, this is defined as the amount of force applied on an object displaced on a longitudinal unit. Mathematically this is

$W = \vec{F} \times \vec{d}$

Here,

F = Force vector

d = Displacement vector

Of all the options presented, only in the last one there is no change in distance, so the work done there is zero.

The correct option is 5.