Do Now

Do Now Take back your quiz

I can guarantee you will see these questions again (midterm, Quest, etc.)

Go through your HW, notes (Do Nows, Exits, POGILs, etc) and HIGHLIGHT where you can find the solutions to every one of your quiz questions (for the majority of them, its word for word) As you are highlighting, MAKE CORRECTIONS.Check in with me when you are stuck.

HW: Prep for your QUEST next class!ID NAME DATE Ch 7 Quiz

1. Scale of 1 to 5 (1 being the least) how confident are you for next class Quest? EXPLAIN 2. Reflect after getting back your quiz: did you make silly errors? Did you focus in class? Did you put your full time and effort into your HW (BOTH the reading/ studying AND written?) Were you prepared? Etc. Give me COMPLETE, HONEST feedback regarding your thoughts (not simply yes or no answers.full sentences!!!)When is impulse larger? (heads down hands up)

When objects bounceWhen objects dont bounce Doesnt matter either way Not sure!

BouncingImpulses are greater when bouncing takes placeFt = (mv)Falling flower pot hits your head Momentum stopsFalling flower pot hits your head and bounces off Momentum is reversed. **Impulse to stop < impulse to throw it back again**2(mv)Karate chopPelton wheel

44BouncingImportant point: It only takes an impulse of mv to stop the ball. It takes twice the impulse (2mv) to make it bounce)

Think about a bouncing ball:Before it hits the ground:Speed = vMomentum = mvAt the moment it hits the ground:Speed = 0Momentum = 0After it leaves the ground:Speed = vMomentum = mvImpulse needed to stop the ball = mvTotal Impulse = 2mvImpulse needed to accelerate the ball upwoard = mv

Just like the medicine ball exercise!!!

If the time of impact is long, the force will be milder. If the time is very short, the force is powerful. When things bounce off an object after hitting them, it is even more deadly in force magnitude.The physics term forBOUNCEis REBOUNDA rebound is a special type of collision involving: A rebound is a special type of collision involving: a direction change which results in a velocity change. A rebound is a special type of collision involving: a direction change which results in a velocity change. Observe that the greater therebound effect, the greater theA rebound is a special type of collision involving: a direction change which results in a velocity change. Observe that the greater therebound effect, the greater theacceleration, momentum change, and impulse.

A rebound is a special type of collision involving: a direction change which results in a velocity change. Observe that the greater therebound effect, the greater theacceleration, momentum change, and impulse.

The result of the direction change is a large velocity change.

HW that was due last week#11-13, p. 100 Texts open if needed PAY ATTENTION as we rapidly review! (need to conserve time with the snow day!)

HW that was due last class#11-13, p. 100 Texts open if needed we are rapidly popcorning!

11a) Visualize yourself on a skateboard. When you throw a ball, do you experience an impulse?

Yes push the ball, and ball pushes you (force) for an amount of timeforce x time = impulse!

HW that was due last class11b) Visualize yourself on a skateboard. When you catch a ball, do you experience an impulse?

Yes push the ball, and ball pushes you (force) for an amount of timeforce x time = impulse!

HW that was due last class11c) Visualize yourself on a skateboard. When you catch a ball, and then throw it back, do you experience an impulse?

Yes push the ball, and ball pushes you (force) for an amount of timeforce x time = impulse!

HW that was due last class11d) Visualize yourself on a skateboard. In which of the scenarios do you experience the largest impulse?CatchThrowCatch and throwSame in all

Catch and throw its like bouncing! More velocity change, so more momentum change, so more impulse!

HW that was due last class12) Why is more impulse delivered when bouncing occurs?

More velocity change, so more momentum change, so more impulse!

HW that was due last class13) Why is the Pelton wheel an improvement over a wheel with flat blades?

QuestionWhy 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.2020QuestionWhat are two ways that crumple zones in cars minimize the effect of force in a collision?

Crumpling increases the time over which the momentum is changed, thus decreasing the force.

Crumpling means less likely to rebound, thus less impulse.2121Question2 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.

2222Free WriteI am going to show you a series of scenarios, and tell you whether they are considered to be elastic or inelastic collisionsIt is your job to write/draw the scenarios you see on your T chart Then, comparing your columns, I want you to create a definition for elastic collision and inelastic collision.

ExamplesRemember, WRITE/DRAW what you observe with enough detail to know whats going on later when you look at these notes!Newtons Cradle elasticWhat happens if I release1? 2? 3? 4? 1 &1? Etc.Bouncy Ball elasticGlob of putty- inelasticNotice what happens to the side of the putty that is dropped onto the deskCars with Velcro facing- inelasticNotice what happens if one is at rest, and one is moving toward the other.or, both move toward each otherCars with magnets facing- elasticNotice what happens if one is at rest, and one is moving toward the other.or, both move toward each otherBilliards (pool) elasticCar crash - inelastic

Create your definitions! Volunteers to share your definitions? Elastic InelasticBounceNot deformed after collision

Dont BounceStick deformed after collisionNeed a FORCE to get them back to normal

Key Point?Momentum is ALWAYS conserved, in bothELASTIC

and INELASTIC collisions

What does CONSERVED mean?Stays the sameDoesnt change Total Momentum BEFORE collision= Total Momentum AFTER collision

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.

11In the absence of an external force, the momentumof a system remains unchanged. The momentum lost by an object in a closed system will be gained by other objects so that the totalmomentum 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.

In hockeyMomentum 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.

OrMomentum 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.)EXAMPLE:Cars with velcro demo

The first car has a certain amount of momentum (mv) Using numbers (1 * 1) = 1

After collision, the MASS doubles.and the velocity halves (2m * v) Using numbers (2 * ) = 1

But still the same TOTAL momentum!Total Momentum BEFORE collision= Total Momentum AFTER collision

We are going to try one together

From now until the end of classFinish the BACK of the worksheet you just receivedCheck in with us when you are done (NOT reviewing as a class)Meet in pairs or groups to REVIEW the HW that was due todayCheck in with us regarding any questions