1. Momentum and Collisions
AP Physics Review
Momentum and Collisions

2. Momentum Momentum(p) is a function of an objects mass and velocity.
An objects resistance to changing motion is called its inertia and that is strictly dependent upon the objects mass. However an object with a large mass with a tiny velocity mass be easier to stop than a small mass with a large velocity.
p = mv units are kg m/s

3. Impulse and Change In Momentum
F = ma and a=v/t
So F=m(v/t) or F = (mv)/t or F = p/t
This leads to Ft = Δp
Ft = J which is the impulse (units Ns or kgm/s)
This impulse will change an objects momentum.
Impulses can be either positive or negative therefore increasing or decreasing an objects momentum.
Friction acting over time would bean example of a negative impulse.
A thruster on a rocket acting over time would be an example of a positive impulse.
Watch for positive and velocities for Δp

4. Conservation of Momentum
Assuming there are no outside forces acting on the system, during a collision, momentum must be conserved.
ΣMomentum before = ΣMomentum after
‘ signifies the final property of the object.
Because velocity is a vector, momentum is as well. Watch for negative velocities due to direction.

5. Elastic Collisions Objects collide and bounce apart.
In this type of collision momentum is conserved as well as kinetic energy.
The total initial momentum and kinetic energy are equal to the total final momentum and kinetic energy.
The equations below can be rearranged to solve for one unknown in terms of the others and the substituted into the other equation.

6. Inelastic Collisions Objects collide and stick together.
Momentum is conserved but kinetic energy is NOT conserved. Some energy is lost to heat and deforming the objects.
Equation for the momentum is as follows.