Question

If a body of mass 2 kg changes its momentum from 25 kgm/s to 18 kgm/s in 0.14 s.
Then calculate the force acting on the body.

Answer 1

Given:-

→ Mass of the body = 2kg

→ Initial momentum = 25 kgm/s

→ Final momentum = 18 kgm/s

→ Time taken = 0.14 s

To find:-

→ Force acting on the body.

Solution:-

[Note : In this problem, we have no use of mass of the body.]

By Newton's 2nd law of motion, we know that :-

=> F = Δp/t

=> F = m(v - u)/t

∴ F = mv-mu/t

Where :-

• F is the force acting .

• mv is final momentum of the body.

• mu is initial momentum of the body.

• t is time taken.

By substituting values, we get :-

=> F = 18 - 25/0.14

=> F = -7/0.14

=> F = -700/14

=> F = -50 N

[Here, -ve sign represents retarding force]

Thus, force acting on the body is -50 N or a retarding force of 50 N .

Some Extra Information:-

2nd law of motion: The rate of change of momentum is directly proportional to the force applied and it will take place in the direction of force.

i.e. F ∝ Δp/t