Question

The impulse of a force is equal to the change in ____________.
A) mass
B) velocity
C) momentum
D) energy

Answer 1

Hint: An impulsive force refers to a large force that acts on a body for a short duration of time. This force, however, will produce a finite change in the momentum of the body. A typical example of this force is when a ball gets hit by a batsman. The force acting on the ball is only for the instant at which the ball and the bat are in contact. But the hitting of the bat has changed the momentum of the ball.

Complete step by step answer:
Using a physical example, describe the impulse of a force.
Consider the case when a ball hits a wall and bounces back. Here, the force acting on the ball, when the ball and the wall are in contact with each other, is for a very short interval. But still, the exerted force was large enough to reverse the momentum of the ball. In this scenario, the force acting on the ball and the time interval for which the ball and the wall were in contact is not easy to be determined. But the change in momentum of the ball is measurable. This change in momentum is termed as an impulse.
Impulse is defined as the product of the large force acting on a body and the time of action.
The impulse is given by,
$J = Ft$ where $F$ is the force acting on the body and $t$ is the time of action of the force.
Or,
$J = \Delta p$ where $\Delta p$ is the change in momentum of the body.

Hence the correct option is C.

Note:
When the momentum of the ball in our example got reversed, it is the direction of its velocity that reversed. Thus the change in momentum of the ball is twice its initial momentum. As the impulsive force acts only for a very short time, we can assume that the position of the body does not undergo any appreciable change during the action of the force.