1. Physics 11 Advanced
Mr. Jean
May 7th, 2012

2. The plan: Video clip of the day Conservation of Momentum Loose Cannon?
Collisions at a glance part #1

3. One Dimensional Collisions:
In a one dimensional collision both the magnitude and the direction of the momentum must be conserved.
For complex momentum situations break all momentums into components and then sum the components. This too will conserve momentum.

4. Collisions:
Collisions can be classified according to the energy interaction that takes place:
Elastic collision  kinetic energy is conserved
Inelastic collision  kinetic energy is not conserved
Perfectly inelastic collision  objects stick together and have the same velocity.

5. Example:
An old lady driving a 2.5x103 kg H2 Hummer drives into the back of your 1.0x103 kg Mazda RX8. The two cars stick together. What is their velocity after the collision if the old lady was originally travelling at 8.0m/s?

7. Example #2:
The cue ball collides with the ‘8’ ball. The cue ball has twice as much mass as the ‘8’ ball. The objects do not stay attached.
What is the velocity of the ‘8’ ball?
Is this collision realistic? (Why or why not?)

9. Cannon Recoil:
A 2000kg cannon contains a 100kg armour piercing shell. The cannon fires the projectile horizontally with a velocity of 1000m/s.
What is the velocity of the cannon after the shot?

12. “Loose Cannon”:
An unpredictable person or thing, liable to cause damage if not kept in check by others.
Also a place to eat in Halifax on Argyle Street.

13. Rifle Recoil:
.50 Cal Rifle
“Surprising Recoil”

14. Glancing Collisions:
Glancing collisions: This type of collision takes place in two dimensions. Collisions on a pool table are good examples of this type of collision. Momentum still has to be conserved – it’s the law for crying out loud!
But the problems can become fairly complex. One technique to keep track of what’s going on is to break things into x and y components:

15. Momentum is still conserved:

16. Glancing collisions:
We will deal with greatly simplified collisions. Basically with right angles and one of the bodies at rest at the beginning.
Example: An 8.00 kg mass moving east at 15.0 m/s strikes a 10.0 kg mass that is at rest. The 8.00 kg mass ends up going south at 4.00 m/s.
(a) What is the velocity of the second ball?

17. Billiard Ball Collisions:

18. a) We analyze the momentum in the x and y directions.
The x direction:
This is because the second body has no initial velocity so it has no initial momentum in either the x or y direction.
After the collision, the first body has momentum only in the y direction, so the x direction momentum after the collision involves only the second body.

20. Now let’s look at the y direction:
The first body’s initial motion is only in the x direction, therefore it has no initial momentum in the y direction. The second body is at rest at the beginning so the total initial y direction momentum is zero.

21. Y-component:
Now we can solve for the velocity of the second body using the Pythagorean theorem

22. So ball #2’s total velocity:
Now we find the angle :
Trigonometry is just the thing to find the old angle:

23. To do:
P. 315
Questions 25 26
P. 317 28 29