Question

A force of 500N is applied to an object to change its momentum by 2000 kg m/s.For how long was the force applied?

Answer 1

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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=mF=1000500=0.5ms−2 

To find initial velocity , consider the equation of motion v2=u2+2 as

Since the body is retarding a=−0×5ms−2 and since it comes to rest v =0

∴0=u2+(2×(−0×5)×64)0=u2−(1×64)⇒u2=64⇒u=64=8ms−1Tofindthetimetaken,considertheequationofmotionv=u+at0=8−0×5×t⇒t=0.58=16s∴u= 8 ms−1, t=16sanda=−0×5ms