Question

A 75 kg person pushes on a wall with a force of 150 N for 2 seconds, after which there is not net force on the person. How fast is the person going after those 2 seconds?

Answer 1

Mass of the person = M = 75 kg

Force with which the person pushes on the wall = F = 150 N

The wall will exert the same magnitude of force on the person.

Time period for which the person pushes on the wall = T = 2 sec

Impulse of the force on the person = I

I = FT

Initial speed of the person = V₁ = 0 m/s

Speed of the person after 2 sec = V₂

Impulse is equal to the change in momentum,

I = MV₂ - MV₁

FT = M(V₂ - V₁)

(150)(2) = (75)(V₂ - 0)

V₂ = 4 m/s

Speed of the person after those 2 seconds = 4 m/s