Question

A box is pushed a horizontal distance of 3.00 m with a force of 200.0 N. The friction force between the floor and the box is 150.0 N.
(a) How much work is done by pushing the box? Answer Answer
(b) How much work does the friction force do? Answer Answer
(c) How much work does the force of gravity do? Answer Answer
(d) How much is the net work?

Answer 1

Horizontal distance, x = 3.00 m

The force with which the box is pushed, F = 200.0 N

Friction between the box and floor, f = 150.0 m

Work done, W = Fx cosθ where θ is the angle between the direction of force and displacement

(a)

Θ = 0 degree

Work, W1 = Fx cosθ = 200 x 3 x cos0 = 600.0 J

Work done in pushing the box, W1 = 600.0 J

(b)

Θ = 180 degree as friction acts opposite to motion

Work done by friction, W2 = f x = -150.0 x 3.00 = -450.0 J

Work done by friction, W2 = - 450.0 J

( c)

Θ = 90 degree as gravity acts perpendicular to the horizontal motion

Work done, W2 = Fx cosθ = Fx cos90 = 0

Work done by gravity, W3 = 0 J

(d)

The net work done, W = W1 + E2 + W3 = 600 - 450 + 0 = 150 J

The net work done, W = 150.0 J