Question

2
A force of 12 N starts acting on a body kept at rest. Find the momentum of the body at
1 s, 2 s and 5 s after the force starts acting.
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Answer 1

Answer:

12 =dp/dt

12=dp/1+2+5

p=96

Answer 2

Answer:

at 1sec p=12kgm/s at 2sec p=24kgm/s at 3sec p=36kgm/s

Explanation:since the body is at rest initially,therefore u=0m/s and hence,initial momentum mu=0kgm/s.

According to newton's second law of motion,F=change in momentum/time

         at 1sec,F=mv-mu/t=mv-0/1,as we know F=12N acting on a body kept at rest.therefore,12=mv-0/1

                   mv=12kgm/s

        at 2sec,F=mv-mu/t=mv-0/2,putting the value of F=12N we will get mv=24kgm/s

           at 3sec,F=mv-mu/t=mv-0/3,similarly as in both the cases we have done putting the value of F=12N we will get mv=36kgm/s