Work done

A block is pulled along a horizontal bench at a constant velocity of 10 ms-1 by a force of 5 N. What is the work done against friction in 4 seconds
Displacement s = v t
= 10 x 4
= 40m

Work done W = F s
= 5 x 40
= 200J

the total power generated against the frictional force
=F x v
=5 x 10
=50 W

so the work done against friction
=P x t
=50 x 4
=200 J