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Selina Solutions Class 9 Physics Solutions for Exercise 3C in Chapter 3 - Chapter 3 Laws Of Motion

Question 26 Exercise 3C

A force of 10N acts on a body of mass 2kg for 3s, initially at rest. Calculate: (i) the velocity acquired by the body, and (ii) change in momentum of the body.

Answer:

Given: F=10N, m=2kg, t=3s; initial velocity u=0m/s

(i) To find final velocity v;

F=ma

a=F/m = 10/2=5m/s2

We know the 1st equation of motion;

v=u+at

=0+(5x3)

v=15m/s

(ii) To find change in momentum

Momentum change = final momentum – initial momentum

Δp=m(v-u)

=2(15-0) = 30 kg m/s

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