Definitions/Terms
Momentum
The amount/quantity of motion that something has
Basic Equation of Momentum
p=mv
A 3 kg toy car moves at 2 m/s.
What is its momentum?
6 kg*m/s
Impulse
Change of momentum over a period of time
Conservation of Momentum Equation
P(Intial)=P(Final)
A 0.2 kg tennis ball hits a racket and changes speed from 0 to 30 m/s in 0.1 seconds.
What average force was applied?
Conservation of Momentum
The total momentum of a system will always remain constant
Impulse Equation
J=FΔt
A 5 kg cart moving at 2 m/s collides with a 3 kg cart at rest. After the collision, the 5 kg cart slows to 1 m/s.
What is the final speed of the 3 kg cart?
1.67 m/s
Elastic Collision
A collision in which momentum and KE are constant
Impulse-Momentum Theorem
J=Δp=mΔv
A 1.5 kg object moving at 4 m/s hits and sticks to a 2.5 kg object at rest.
What is their final speed together?
1.5 m/s
Recoil
Results of Newtons 3rd Law, Conservation of Momentum
Inelastic Collision
m1v1i+m2v2i=(m1+m2)vf
A 0.1 kg rubber ball hits a wall at 10 m/s and bounces straight back at 8 m/s. The contact time is 0.05 seconds.
What was the average force on the ball?
-36N