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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»


Solution :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`


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