Question

If impulse is?
A- Infinity, the momentum of the body becomes infinite
B- Negative, the momentum of the body increases
C- Negative, the momentum of the body decreases
D- Zero, the momentum of the body becomes zero

Answer 1

Impulse is defined as a very large force acting for a very short time. Impulse can be written as: $j=Ft$. The dimensions of RHS gives us the units of momentum, thus we get to know that impulse can be defined as the change in the momentum of the body. Impulse is a vector quantity.

Complete step by step answer:
We know impulse is given as the change in momentum. Now we have 4 different conditions, let us check them one by one.
Impulse in terms of momentum can be written as: $j=m \Delta v$
When the impulse is infinity, $j=m \Delta v$ , then either mass is zero or the change in velocity is zero. So, option (A) is incorrect.
When the impulse is negative $j=m \Delta v$ mass can never be negative, so the change in velocity comes out to be negative. But in that case the momentum of the body decreases, thus, option (B) is incorrect.
If impulse is negative, it shows that the impulsive force acting on the body is negative. So, if force acting on the body is negative, then the momentum of the body definitely decreases.

So, the correct answer is “Option C”.

Note:
Don’t get confused between momentum and the change in the momentum. For example, consider the option (D). If the impulse of a body is zero,$j=m \Delta v$ , then since mass can never be zero, it means the change in the velocity is zero and in that case the change in the momentum of the body will eventually be zero. But momentum will be non zero, so option (D)