1. Day 43 In AP Physics… Nearing the halfway point of this year
1) Handout of the Q2 Exam info
2) You do a series of tough examples with springs based on what we have learned
3) We learn about ballistic pendulums, their purpose, and the physics behind them

2. Handout
This is simply a brief review of the older concepts of this quarter.
You are responsible for doing more. I will be doing a modified review next class
Remember: It is not about being able to use an equation. It’s a lot more about being able to interpret, manipulate, and reason.

3. Start with 22, 23 and 24 alone on a separate piece of paper
Start with 22, 23 and 24 alone on a separate piece of paper. For each, write a sentence as well explaining the reason.
Ignore 39 for now

4. Now discuss with each other on those 3, come to a conclusion
Voting:

6. Voting

8. Voting

10. Now try 39 alone.
Compare to partners, come to conclusion
VOTE

11. On the practice AP, this was the most ‘mathy’ of the multiple choice

12. Now for the free response. 25 minutes. You go.

16. Now for a change of perspective…
Scientific approach on ballistics
1742, Benjamin Robins was involved with the improvement and application of gunnery accuracy, design and testing
His book was the first use of calculus in military theory.

17. One thought: How can you determine the muzzle velocity of a gun or cannon?
Robins thoughts:
Way One: Measure the recoil, use momentum and impulse to find the proportional velocity. Problem: instruments unable to do this.
Way Two: Shoot the bullet/ball into a block connected to a rope, measure how high the pendulum goes.

18. The bullet is shot at velocity V1 and almost immediately hits the block, transferring momentum to the block.
The block-bullet system now moves at V2 and goes in an arc, slowing as it rises to a maximum height h.

19. There is a large loss of system energy during the hit, so MEbefore > MEafter , which means we cant assume the Kinetic energy of the bullet is the same as the Gravitational potential at the max height.
The momentum of the bullet right before the hit is equal to the momentum of the block-bullet system after.

20. So for example, a 20gram bullet hits a 2kg block and goes up 30cm
So for example, a 20gram bullet hits a 2kg block and goes up 30cm. How fast was it going right before it hits?

21. Our work

22. Draw a LOL bar chart for the bullet/block system