Question

A car was moving with a constant velocity of 50 m/s. After brakes were applied, it travelled a distance of 30m then it stoped. Find the work done by brake if mass of the car is 1500 kg.

Answer 1

Answer:

vsquare - usquare = 2as

0 - 2500 = 2×a×30

a = 2500/60

a= 41. 66

force = mass/ a

= 1500/ 41.66

= 36joule

work done = f × s

= 36×30

= 1080

Answer 2

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initial velocity(u)=50m/s

final velocity(v)=0

distance(s)=30m

mass(m) of the car=1500kg

now...the retardation applied by the brake is =a (let)

now..from the relation ..

v²=u²-2as

0=50²-2(a)(30)

a=50²/60

a=(125/3)m/s²

now the work done by the car...

w=FS=(ma)s=[1500×(125/3)×30]Joule

$= 1.875 \times 10 {}^{6} joule$

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