Question

Why is force is said to be the rate of change of momentum and not the change in velocity?

Answer 1

Rate of change in momentum:

1. The rate of change in momentum of an item is proportional to the applied resultant force and is in the same direction as the applied resultant force. So, we can say that the rate of change of momentum is equal to the force applied
2. It is understood that, $\mathrm{Momentum}=\mathrm{mass}\times \mathrm{velocity}$.
3. Differentiating this formula with respect to time gives, $\mathrm{force}=\mathrm{mass}\times \mathrm{acc}e\mathrm{leration}$.

Therefore, it says that change in momentum can be referred to as force. But the change in velocity can be referred to as acceleration, not force.