Thursday, December 12, 2013

1. By the end of the day today, IWBAT… • Explain how momentum is conserved • Do Now: Thursday, December 12, 2013

2. By the end of the day today, IWBAT… • Explain how momentum is conserved Why it matters in LIFE: Momentum alone is a fairly easy topic – adding impulse takes this unit on momentum to the next level which makes us higher-level thinkers! Why it matters in THIS CLASS: Unit #7 Content  approximately ½ of your upcoming Final Exam

3. What it might look like on a test:

4. Agenda + Announcements

5. Review • What is momentum? • If an object is at rest, does it have momentum? • What two factors does momentum depend on? • What is the equation for momentum? • What are the units for momentum? • What is the variable for momentum? • If I double an object’s mass and keep its velocity the same, what will happen to its momentum? • If I double an object’s velocity but keep mass the same, what will happen to its momentum?

6. Review • If I double the velocity and cut the mass in half, what will happen to the momentum? • How do you stop an object with momentum? • Compare the forces I would need to exert to stop a bowling ball and a tennis ball traveling at the same speed. • When an object’s velocity changes, so does its… • What is the name for a change in momentum? • What is the equation we use to represent impulse? • Give me 2 examples of impulses.

7. Thursday, 12/12/13 Put this into your table of contents!

8. Conservation • Conservation = conserve • Environmental conservation • “Conserve your energy!” • Conservation of Mass • The Law of Conservation explained….. “Conservation” means “constant” or “unchanged”

9. The Law of Conservation of Momentum When two objects collide, the total momentum of the objects before the collision is equal to the total momentum of the objects after the collision. The momentum lost by object 1 is equal to the momentum gained by object 2.

10. Law of Conservation of Momentum in Action

11. Think, Pair, Share • Suppose that a medicine ball is thrown to a clown who is at rest upon the ice with a velocity of 10 m/s. The clown catches the medicine ball and glides together with the ball across the ice. The mass of the medicine ball is 5 kg and the mass of the clown is 60 kg. • What is the total momentum of the system before the collision? • What must the total momentum of the system be after the collision? • If the clown and the medicine ball move together as a single unit after the collision, what happened to the velocity of the medicine ball? Why?

12. Figure it Out! • A 25 kg car moving to the right at 5.5 m/s collides with a 35 kg car moving to the right at 2 m/s. After the collision, the 25 kg car slows to 1.4 m/s to the right. What is the velocity of the 35 kg car after the collision? • A 76 kg boater initially at rest in a stationary 45 kg boat, jumps out of the boat and onto a dock. If the boater jumps with a velocity of 2.5 m/s to the right, what is the final velocity of the boat? • A 3500 kg truck going 25 m/s east runs into a 550 kg motorcycle stopped at a stop sign. If the truck stops as a result of the collision, how fast will the motorcycle shove forward?

13. The Equation TOTAL Momentum before = TOTAL Momentum after pi = pf m1v1,i + m2v2,i = m1v1, f + m2v2, f Initial momentum of 1st object Initial momentum of 2nd object Final momentum of 2nd object Final momentum of 1st object

14. Now let’s answer it! Choose the correct answer, then paraphrase the statement in your C Notes!