A car weighing 1000 kg is travelling at the speed of `15ms^(-1)`. It decelerated due to brakes applied and stops after covering a distance of 25 m. Find the force exerted by the brakes and the work done by the brakes.

Answer

The force exerted by the brakes is 4500 N.
Work done by the brakes is 112500 J.

Explanation

Here, `m=1000kg,u=15ms^(-1),v=0,`
`s=25m`
`v^(2)-u^(2)=2as`
`therefore 0-(15)^(2)=2axx25`
`therefore -225=50alpha`
`therefore a=-(225)/(50)=-4.5ms^(-2)`
Negative acceleration means deceleration.
`therefore` Deceleration `=4.5ms^(-2)`
Decelerating force `F=ma`
`=1000kgxx4.5ms^(-2)`
`=4500 N`
Work done by the brakes,
`W=Fs`
`=4500kgxx25m`
`=112500J`