1. Momentum and collisions
Ch 6
Momentum and collisions

2. Momentum
Mass in motion

3. Momentum Mass in motion Vector units: kilograms x meters per second
Momentum = mass x velocity
p = m v
Vector
units: kilograms x meters per second
kg m s-1

4. Momentum
Momentum is related to kinetic energy
KE = ½ mv2
KE = p2/2m

5. Momentum Momentum is related to net force net F = ma
net F = m(Δv/Δt) = Δp/Δt

7. Impulse
Change in momentum
vector

8. Impulse
Impulse = change in momentum
I = Δp
I = mv2 - mv1

9. Impulse
In order to change an object’s momentum, the velocity needs to change
Change in velocity is acceleration
Acceleration requires a net force
The longer the object is exposed to that net force, the greater the change in momentum will be
I = netF Δt
netF Δt = Δp
Units: Ns

10. Impulse due to a variable force

11. Conservation of Momentum

12. Collisions Elastic https://www.youtube.com/watch?v=0LnbyjOyEQ8
Objects collide and separate after the collision
e.g. pool balls
“in a perfect world” Both momentum and kinetic energy are conserved
p1i +p2i = p1f + p2f
m1v1i + m2v2i = m1v1f + m2v2f
KE1i + KE2i = KE1f + KE2f

13. Collisions Inelastic https://www.youtube.com/watch?v=oQ7VR7QaG8A
Momentum is conserved, but kinetic energy is not
Perfectly inelastic: objects collide and stick together
p1i + p2i = p1f + p2f
m1v1i + m2v2i = vf(m1 + m2)