This week, we will use the concept of momentum
to analyze some more advanced situations.
Namely, systems in which there is a continuous flow of mass
rather than just the motion of discrete objects.
The classic example of this is the thrust
due to exhaust from a rocket engine.
Once again, we will appeal to a differential analysis
technique.
Breaking the flow down into a large number of small elements,
analyzing one of the elements in detail, and then generalizing.
This is an important example of a situation where
the point mass form of Newton's Second Law of Motion-- f equals
ma-- is inadequate, and one must instead
use the more general form of the law-- f
equals dpdt-- or the force is equal to the time
derivative of the momentum.