Question

9. A box is initially at rest on a horizontal,
frictionless table. If a force of 10 Newtons
acts on the box for 3 seconds, what is the
momentum of the box at the end of 3
second interval ?
(1) 30kg-m/s
(2) 60kg-m/s
(3) 90kg-m/s
(4) 15kg-m/s​

Answer 1

3 is the correct answer ✌

Answer 2

Given:

Initial velocity (u) of the box = 0m/s

Magnitude of force acting = 10N

Time during which force is applied= 3s

To find:

The momentum of the box at the end of 3  second interval

Solution:

We know that force is change is momentum per unit change in time.

Hence, F = dP/dt

Cross multiplying and integrating,

∫Fdt = ∫dP

or P = ∫Fdt

Since the force is constant,

P = F.t

= 10x3

=30 kg-m/s

Hence, the  momentum of the box at the end of 3  second interval is 30 kg-m/s.