In a collision, is the net impulse experienced by an object equal to its momentum change?
Yes. Impulse is defined as the change in momentum over an arbitrary time interval, or equally as the average force times the difference in time.
You can see from the second equation why the unit of impulse is typically the Newton-second. (
If you know an object's initial momentum and its final momentum, the impulse is given by the difference between the two values.