Do Now I am not collecting HW today. Take back your quiz I can guarantee you will see these questions again (midterm, Quest, etc.) Go through your HW, notes (Do Now’s, Exits, POGILs, etc) and HIGHLIGHT where you can find the solutions to every one of your quiz questions (for the majority of them, it’s word for word) As you are highlighting, MAKE CORRECTIONS. Check in with me when you are stuck.

Question 2 cars are involved in a collision. Which would be more damaging - if the cars collide and bounce or collide and crumple? Collide and bounce. The momentum change is larger and therefore there is a greater impulse and greater force.

Question What are two ways that crumple zones in cars minimize the effect of force in a collision? 1.Crumpling increases the time over which the momentum is changed, thus decreasing the force. 2.Crumpling means less likely to rebound, thus less impulse.

Question Why is falling on a floor with more give less dangerous than falling on a floor with less give? The floor with more give allows a greater time for the impulse that reduces the momentum of the fall. A greater time for changing momentum means less force.

Take out your Elastic and Inelastic collision notes from last class. We are now going to define what these collisions actually are. (turn the page)

QualitiesELASTICINELASTIC Describe how they collide – bounce, stick together, etc… Bounce Stick What happens to the momentum after collision? Is it conserved? Is it shared, or transferred… Always conserved! **It’s the LAW** Always conserved! **It’s the LAW** Are the objects deformed post- collision? Nope! Yep! As long as there is no external force, there is no way to get them back to normal… Is heat generated during the collision? No – there is no such thing as perfectly elastic collision that we can SEE, because there is always SOME friction Yes – friction! Give real life examples: TECHNICALLY…Subatomic particles colliding But the closest thing we can see to it would be something like billiards TECHNICALLY…Everything we can see with our bare eyes But the closest thing we can see to it would be something like a car crash

Series of questions from your HW last night… Heads down, answers

If 2 objects of EQUAL mass experience an ELASTIC collision… 1.Momentum IS conserved 2.Momentum IS NOT conserved 3.Not quite sure

If 2 objects of UNEQUAL mass experience an ELASTIC collision… 1.Momentum IS conserved 2.Momentum IS NOT conserved 3.Not quite sure

If 2 objects of EQUAL mass experience an INELASTIC collision… 1.Momentum IS conserved 2.Momentum IS NOT conserved 3.Not quite sure

If 2 objects of UNEQUAL mass experience an INELASTIC collision… 1.Momentum IS conserved 2.Momentum IS NOT conserved 3.Not quite sure

Key Point? Momentum is ALWAYS conserved, in both ELASTIC and INELASTIC collisions

Momentum is a conserved quantity in physics. This means that if you have an object or several objects in a system, interacting with each other, but not being influenced by any forces from outside of the system, then the total momentum of the system does not change over time. 11

In the absence of an external force, the momentum of a system remains unchanged. The momentum lost by an object in a closed system will be gained by other objects so that the total momentum will remain the same in the system. Law Of Conservation Of Momentum Closed System: No matter or energy is allowed to enter or leave the system.

The separate momenta of each object within the system may change. One object might change momentum, while another object changes momentum in an opposite manner, picking up the momentum that was lost by the first.

Conservation of Momentum Momentum = 0 before the shot And after the shot Cannon’s momentum Shell’s momentum (equal and opposite)

Before collision: 1.The momentum of the cart is 60 kg*cm/s 2.The momentum of the dropped brick is 0 kg*cm/s 3.The total system momentum is 60 kg*cm/s. After collision: 1.The momentum of the cart is 20.0 kg*cm/s 2.The momentum of the dropped brick is 40.0 kg*cm/s 3.The total system momentum is 60 kg*cm/s. 4.The momentum lost by the loaded cart (40 kg*cm/s) is gained by the dropped brick.

In hockey…Momentum is transferred from the stick to the puck. The momentum lost by the stick is equal to the momentum gained by the puck. The total amount of momentum stays the same. Or…Momentum is transferred from player to player. (The momentum lost by one player is equal to the momentum gained by the other. The total amount of momentum stays the same.)

Go to this Page in your Pogil 

Remember…key point is MOMENTUM BEFORE = MOMENTUM AFTER Fill this in!!! Elastic  INelastic 

We are going to try one together…

(80 * 3 ) + (42 * 0) = ( ) vf (240) + (0) = (122) vf 240 kg m/s = (122 kg) vf Divide both sides by 122 kg, and vf = ~ 2m/s

Data from Collision Java Activity Take out your data from last class Pick your data from ONE of the ELASTIC COLLISIONS and check via formula. Repeat with data from ONE of the INELASTIC COLLISIONS and check via formula. BEFOREAFTER Mass of Wagon 1 Mass of Wagon 2Mass of Wagon 1Mass of Wagon 2 Velocity of Wagon 1 Velocity of Wagon 2 Velocity of Wagon 1 Velocity of Wagon 2 Total Momentum:

Quest Prep I am not collecting these, but here are your options for Quest Prep… (all worksheets also online) Want more practice with conservation of momentum formula? On the back of your web quest, try the problems listed ( p. 100, #22, 27, 35, 37) Need more math practice in general, including conservation of momentum? Go here for problems AND written as well as spoken solutions (also linked on my website) tinyurl.com/RHSmomentumMATH Or try these on page : #24, 29, 32, 34 & 36 Need more conceptual practice? Finish the back of the Granny/Ambrose worksheet, and see me for another conceptual review worksheet