2. ∆ Any object in motion has momentum, “Mass that moves”
Momentum = mass x velocity
is a vector quantity, with same direction as the velocity component.
Symbol, P unit, kgms-1
Change in momentum: - ∆

3. Conservation of Momentum
A system is a pair or group of objects that are interacting in some way.
If a system has no external forces acting on it (eg no friction), then the system is isolated. Total momentum in an isolated system is said to be conserved.

6. PhET Collision-lab

7. A car and its driver have a combined mass of 1200 kg.
The car collided with a stationary van of mass 1500 kg.
The car and van locked together after impact and from the marks on the road the police were able to deduce that the wreckage moved at 4.0 m s–1 immediately after the collision.
Calculate the speed of the car just before it collided with the van.

8. A car and its driver have a combined mass of 1200 kg.
The car collided with a stationary van of mass 1500 kg.
The car and van locked together after impact and from the marks on the road the police were able to deduce that the wreckage moved at 4.0 m s–1 immediately after the collision.
State what physical quantity is conserved in the collision.
State the condition necessary for the quantity you have named in (1) to be conserved

9. P = mv Velocity is a vector. Momentum is also. It has a direction.
Imagine two cars on the road.
They have the same mass.
They collide head on at the same speeds.
Mass 1200kg vi 15ms-1
Mass 1200kg vi -15ms-1
Momentum = mass x velocity
P = mv
P1 = m1v1
P2 = m2v2
P1 = 1200x15 kgms-1
P2 = 1200x(-15) kgms-1
P1 = kgms-1
P2 = kgms-1
Velocity is a vector. Momentum is also. It has a direction.
So here the cars collide. The momentum adds to zero. The cars have no momentum therefore the crumpled wreckage is at a standstill.

10. P = mv Pinitial= Pfinal vf = 10ms-1 m2 1200kg v2 20ms-1
Imagine two cars on the road.
They have the same mass.
The other slams into the back of the first and they lock together.....
One is stopped with the brake off.
m1 1200kg v1 0ms-1
m2 1200kg v2 20ms-1
Momentum = mass x velocity
P = mv
P1 = m1v1
P2 = m2v2
P2 = 1200x20 kgms-1
P1 = 0 kgms-1
P2 = kgms-1
So how fast does the wreckage move?
Momentum is conserved so that…
Pinitial=
Pfinal
Pf = 24000kgms-1
= m x vf
24000 = ( ) x vf
vf = 10ms-1

11. Impulse ?

12. Imagine a Squash ball hitting a wall:F -F
F = average force _
t = time of contact
Impulse =
F(t ) _
Impulse is a vector
Its SI unit = N·s = kg·m/s

15. A .20 kg ball is going 3.0 m/s before it hits a wall and bounces straight back at a speed of 2.0 m/s. If the ball and wall are in contact for s, find the average force exerted on the ball.

16. In a game of tennis, an incoming ball has a mass of
In a game of tennis, an incoming ball has a mass of .075 kg, and a speed of 15 m/s. When it is hit straight back with an average force of 525 N exerted over a time of .005 s, what is its resulting velocity?