Question

A force is acting on a body of mass 0.4 kg intially at rest for 10 sec and after removal of the force the body moves 100m in 20 sec . What was it's intiall force?

Answer 1

Answer:

0.2 N

Explanation:

Given :

Mass = 0.4 kg

In first case :

u = 0 m / sec

t = 20 sec

We have :

v = u + a t

v = 0 + 20 a

v = 20 a .

For second case :

v become initial velocity :

u = 20 a

t' = 10 sec

s = 100 m

We have :

s = u t + 1 / 2 a t²

100 = 20 a × 10 + 1 / 2 × a × 10²

1 = 2 a + a / 2

a = 0.5 m / sec²

We know :

F = m a

F = 0.4 × 0.5 N

F = 0.2 N