Here's why:

* Impulse is the change in momentum of an object.

* Momentum is the product of mass (kg) and velocity (m/s).

* Force is the rate of change of momentum, meaning force is measured in kg⋅m/s².

* Impulse is the product of force (N) and time (s).

Therefore, the unit of impulse is N·s, which is equivalent to kg⋅m/s.