1. Introduction to Momentum (P)
Yes it is a vector mister!!!!!
Introduction to Momentum (P)
And you

2. THE LAWS OF PHYSICS 1) Newton (3 laws) (inertia, F=ma, =/opp F)
2) Kepler (3 laws) (orb. Ellipse, =areas in =t, R3/T2 = 1)
3) The conservation of Energy (only conversion of forms - transformations)
4) The Conservation of Momentum!!!!!!

3. Momentum = P = ?????
P = mv
P is conserved for a system with no external forces acting on it (this is an important qualifier)
That means that the total momentum in the starting conditions = the total momentum in the final conditions
Rolling balls demo here…with conceptual equations

4. Some fun examples for you
1) A book sliding across a table
Is P conserved????
It has mass and velocity!
But it has the external force of friction acting on it – so NO P is not conserved!!!!!!!!

5. What about Newton’s Cradle Really good ones will continue for an hour
For that time P is conserved (transferred)
Notice how 1 mass  1 mass
How 2 masses  2 masses
Newton’s cradles demos here...

6. What about KE??? You can not assume KE is conserved
The basic rules to go by are:
In an elastic collision (where things bounce off each other) KE IS CONSERVED
∑ KE prior to collision = ∑ KE after collision
In an inelastic collision (where things stick together after they collide) KE IS NOT CONSERVED

7. How about a simple example
If a 5 kg dog is moving at 3 m/s, what is the:
P ? =
KE? =
mv = 15 kg m/s
½ mv2 = 22.5 J

8. Another example please
Another example please? 50 kg car,10 m/s, 80 kg truck, unknown V – after collision all stopped
Initial momentum = final momentum
(m1v m2v2)o = (m1v m2v2)f
((50)(10) + (80)(?) = (50)(0) + (80)(0)
Therefore V2 initial = m/s !!!
Minus because we are using the coordinate system

9. Try the same calculation to see if KE is conserved
And you will find it does not work out with the same calculated velocities.
Remember the velocities would be squared, so the negative V becomes positive…
It is a mess – but if you do not want to take my word for it, please try it yourself!

10. And that is all (for now) for the momentum intro.
Prior to working on the lab –
Let’s discuss a related topic

11. IMPULSE ( J ) Play slow motion video here
Why is it that the bungee cord does not just pull the jumpers legs off???

12. Impulse = ??? J = F Δt (units are N s )
How are impulse and momentum related????????

13. The Impulse – momentum theorem
F Δt = ΔP = mvf - mvo
Play the Glasgow impulse video here

14. NOW 4 groups work on the lab
The other groups work on the worksheet questions – and work on the lab when it opens up
When the air track groups finish their data collection – they can start on the questions