1. Key Areas covered
Conservation of momentum in one dimension and in cases where the objects may move in opposite directions.

2. What we will do today
State that momentum is the product of mass and velocity.
State the law of conservation of linear momentum.

3. Momentum
T. Ferns – 13/9/04 LO’s 1.2.6, 1.2.7, 1.2.8, 1.2.9, ,

4. Momentum is a vector quantity and is the product of mass and velocity.
Momentum = mass x velocity
kg ms-1
The units of momentum are kgms-1.
Momentum is sometimes given the symbol p.
p = mv The direction of the momentum is the same as the velocity.

5. Experiment Aim: To find our own momentum Results: Distance travelled m
Time taken s
Your Velocity (d/t)
m/s
Your mass kg
Your momentum (mv)
kgm/s

6. Virtual Experiment – Law of Conservation of Momentum
Click link below
Select Mechanics and Properties of Matter
Run
Collisions and Explosions
Use Inelastic collision; elastic collisions; and explosions
Record results on table (next slide)
Virtual Higher Physics

7. Virtual Experiment – Law of Conservation of Momentum
Before
After
m1v1
m2v2
1 x 2 = 2
1 x 0 = 0
1 x 1 = 1
2 x 3 = 6
2 x 1 = 2
1 x 4 = 4
2 x 0 = 0
2 x (-2)= -4

8. Conclusion Momentum is always conserved in collisions.
However, this will only be the case if the direction of momentum is taken into account.

9. The Law of Conservation of Momentum
In any collision or explosion free of external forces, the total momentum remains the same.
This can be applied to the interaction of two objects moving in one dimension, in the absence of net external forces.
For any collision (with no external forces):
Total momentum of = Total momentum of
all objects before all objects after

10. Example
Solution
+ ve
Tot mom Before = Tot mom After
m1v1 + m2v2 = m3v3
(3 x 5) + (2 x -5) = (3 + 2) v3
15 + (-10) = 5v3
v = 5 / 5
v = 1 ms-1 to right
5 ms-1
5 ms-1
3 kg
2 kg
Find the velocity of the trolleys when they stick together after colliding.