A block of mass rests on a smooth horizontal surface

PHYSICS · Subjective · CBSE · Physics · Work, Energy and Power · Work, Energy and Power

Problem

A block of mass

4\,\text{kg}

rests on a smooth horizontal surface. Beginning at

t=0

, a time–dependent horizontal force

F(t)=20t\,\text{N}

(where

t

is in seconds) acts on the block for the next

5\,\text{s}

. (i) Derive an expression for the block's kinetic energy

K(t)

as a function of time during the application of the force. (ii) Obtain an expression for the instantaneous power

P(t)

delivered to the block, and hence find its value at

t=5\,\text{s}

. (iii) Calculate the average power supplied to the block over the complete

5\,\text{s}

interval.