Physics # a body of a mass 500g is moving with a speed 20m/s when brakes are applied it comes to rest in next 0.05s calculate the change in momentum and the average force applied​

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>Application of Newton's Laws of Motion

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A force of 500 N acts on a body of mass 1000 kg and the body is brought to rest within a distance of 64 m. Find the initial velocity and the time taken by the body before to come to rest.

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Correct option is

A

8 ms

−1

,16s

Solution: Force, F= 500 N ; mass of the body, m= 1000 kg.

From newtons second law of motion,

F = ma, where F, m and a are the force , mass and acceleration respectively.

a=

m

F

=

1000

500

=0.5ms

−2

To find initial velocity , consider the equation of motion v

2

=u

2

+2 as

Since the body is retarding a=−0×5ms

−2

and since it comes to rest v =0

∴0=u

2

+(2×(−0×5)×64)

0=u

2

−(1×64)⇒u

2

=64

⇒u=

64

=8ms

−1

Tofindthetimetaken,considertheequationofmotionv=u+at

0=8−0×5×t⇒t=

0.5

8

=16s

∴u= 8 ms

−1

, t=16sanda=−0×5ms

−2

329 