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Momentum Study Guide- Ch. 9 p.p. 228-249
Momentum = p = (mass)(velocity)= mv
[units: kg m/s]
Impulse = (Force) ( time interval) = FΔt
[units: N s]
Impulse = Change in Momentum FΔt = mΔv

If you know the mass and velocity of an object you can calculate its
momentum.

An object’s momentum will change when due to an impulse, an external
force acting on an object for some period of time.

Like acceleration, force and velocity, momentum and impulse have
direction as well as magnitude (amount or numerical value). The
momentum of an object is in the same direction the object is moving. The
impulse is in the direction of the force on the object.

You can calculate the total momentum of a group of objects by adding up
the momentum of each individual object in the group. The group of
objects together is called the “system.” You have to take into account
which way the objects are moving when finding the total momentum of
the system.

The total momentum of a system stays the same as long as no net
external force acts on the system no mass is added or subtracted from the
system. This is the Law of Conservation of Momentum.

A neat thought: If you draw a circle big enough to enclose every object in
the Universe, then you would have a system with no unbalanced forces
(there’s nothing outside of the circle to supply a force). This means that
the total momentum of the whole Universe must stay the same--momentum just changes hands from object to object.
Collision Problem Solving Strategies

Always start by drawing “Before” and “After” pictures of the situation
described in the problem.

Show all known masses and velocities (speed and direction of motion)
beside each object in your diagrams.

If no net force acts on the system, then the sum of all the momentum in
the system is conserved.
Momentum Before
= Momentum After
m1v1 + m2v2 = m1v1’ + m2v2’