Question

A horizontal force of 20N is required to keep
a body moving in a horizontal direction with
constant velocity. What is the work done by
frictional force when the displacement of body
is 2 m?​

Answer 1

Answer:

work done=forceXdisplacement

work done=20NX2m

work done=40J

Answer 2

As the body is moving with constant velocity, thus the net external force acting on the body must be equal to zero.

Hence the friction force must be equal to the external force applied on the body.

∴ Frictional force f=F=10 N (acting in opposite direction to that of velocity)

Distance moved by the body S=2 m

∴ Work done by friction W

f =FScosθ where θ=180 °

W f =FScos180 °

=10×2×(−1)=−20J