A horizontal constant force F pulls a block of mass m placed on a horizontal surface. If the coefficient of kinetic friction between the block and ground is `mu`, find the power delivered by the external agent after a time agent after a time t measured from the beginning of action of the force.

Explanation

The forces acting on the block are `Frarr`, kinetic friction `flarr`, `mgdarr`, and `Nuarr`.

Power delivered by the external agent (force F) is
`P_(ext)=oversetrarrF*vecv=Fvcos0^@=Fv` (i)
we have `v=int adt` (ii)
Since a is decided by the net force
`F_(n et)=(F-f)` (but not F or f)
Force equation:
Using eqs. (i), (ii) and (iii), we have
`P_(ext)=F(int(F-f)/(m)dt)=F((F-f)/(m))t` (iv)
`Law of kinetic friction `f=mumg`
Using eqs. (iv) and (v), we have `P_(ext)=(F(F-mumg)t)/(m)`