In this lesson, I'm going to add a new dimension to momentum and introduce impulse. Impulse
is the change in momentum, meaning the final momentum minus the initial momentum. Since it
involves the momentum both immediately before and immediately after impact, impulse is also equal
to the time of impact multiplied by the force with which the objects collided. Therefore, with
J standing for Impulse, the equation for impulse is:
J = Pf - Po = F * t
Let's do a sample problem involving both impulse and momentum.
An 80N force accelerates a 5kg object from 2m/s to 8m/s.
a. What is the impulse acting?
b. What is the amount of time over which this force is applied?
For part a, we need to use the first part of the impulse equation.
J = (5kg * 8m/s) - (5kg * 2m/s)
J = 30Ns
Now, in part b, we use the answer to part a in conjunction with the second part of the
equation.
30Ns = 80N * t
.375s = t
That's all there is to it. Now, if we had only wanted to know the time, we could have
combined the two previous equations into one and solved for t.
(5kg * 8m/s) - (5kg * 2m/s) = 80N * t
30Ns = 80N * t
.375s = t
In the final lesson of this section, we will discuss angular
momentum.
