Chapter 2 – The Momentum Principle
The Momentum Principle

The change of momentum of a system is equal to the net force acting on
the system times the duration of the interaction

The net force acting on a system at an instant is the vector sum of all the
forces exerted on the system by all the objects in the surroundings at that
instant
Impulse

The change of momentum of a system is equal to the net impulse applied
to it

The product of a force and a time interval is called impulse
Approximating Average Velocity

If the change in velocity is very small over the time interval, the final
velocity can be used as an approximation of the average velocity

If the velocity is changing at a constant rate, which is the case if the net
force is constant, the arithmetic average can be a good approximation
Equations to Know



is an approximation for
Momentum Change with Changing Force

If there is a significant change in force, then break into separate time
intervals and calculate the total momentum
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 Spring '09
 PROG
 Physics, Force, Momentum, net force, momentum principle, Changing Force

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