Question

What is the product of force and time for which force act is called?
A. Momentum
B. Acceleration
C. Inertia
D. Impulse of force

Answer 1

Hint: In order to solve this question we need to understand Force. Force is defined as a push or pull in a body which causes a state change of body, either it brings it in motion or it brings rest. It is mathematically defined from Newton’s second law as force is rate of change of momentum per unit time or force is product of mass and acceleration of the body. If the force becomes zero then the body moves with uniform velocity.

Complete step by step answer:
Impulse is defined as unit force acting over a particular time. So a product of force and time is known as Impulse. This is easier to calculate as physically it represents the area under force time curve which is easier to find as compared to force.It is represented by “J” and is mathematically defined as $J = F.\Delta t$.

It is equivalent to change in momentum and also known as Impulse-momentum relation. as we know from newton’s second law that force can be written mathematically as $F = \dfrac{{dp}}{{dt}}$ and put this relation in impulse formula which is $J = F.\Delta t$ we get,
$J = \dfrac{{dp}}{{dt}}.\Delta t$
$\therefore J = dp$ where impulse is just the change in momentum of a body.

So the correct option is D.

Note: It should be remembered that momentum is defined as product of mass and velocity but its change is defined as impulse because change in momentum signifies change in velocity which equal to product of acceleration and change in time, so change in momentum is equivalent to product of mass, acceleration and change in time, since the force is defined as product of mass and acceleration, so Impulse or change in momentum is defined as product of force and time.