Take one and complete BOTH SIDES. HW Due Place both in In Box (POGIL page 2…… and the worksheet) HW Worksheet – given out at end of class Quest Jan 23 (B day) ***There is a REALLY GOOD review PowerPoint on my website…*** Do Now Take one and complete BOTH SIDES. May work with peers.

TRUE! True FORCES COME IN PAIRS! False Not enough info Not quite sure A bug and the windshield of a fast moving car collide. Tell whether the following statements are true or false, and EXPLAIN your reasoning: a. The forces of impact on the bug and on the car are the same size. TRUE! FORCES COME IN PAIRS! True False Not enough info Not quite sure

SAME FORCE, SAME CONTACT TIME True False Not enough info A bug and the windshield of a fast moving car collide. Tell whether the following statements are true or false, and EXPLAIN your reasoning: b. The impulses on the bug and on the car are the same size. TRUE! SAME FORCE, SAME CONTACT TIME True False Not enough info Not quite sure

A bug and the windshield of a fast moving car collide A bug and the windshield of a fast moving car collide. Tell whether the following statements are true or false, and EXPLAIN your reasoning: c. The changes in speed of the bug and on the car are the same size. FALSE! COMMON SENSE…DO YOU NOTICE THE CAR SLOW DOWN? DOES THE BUG NOTICE A CHANGE? True False Not enough info Not quite sure

TRUE! True False Not enough info Not quite sure A bug and the windshield of a fast moving car collide. Tell whether the following statements are true or false, and EXPLAIN your reasoning: d. The changes in momentum of the bug and on the car are the same size. TRUE! m Δv = m Δv’ Not to mention, Impulse = change in momentum, and we already determined they have the same impulse… True False Not enough info Not quite sure

Bug Windshield Ft m Δv Same Impulse Same change in momentum Diff. masses and velocity changes!

No – not always!! Yes No Not enough info Not quite sure Does a larger force always produce a larger impulse on an object than a smaller force? Explain. No – not always!! F t = F t (1 N) (100s) = (10 N)(5s) 100 Ns = 50 Ns Yes No Not enough info Not quite sure

Yes – throw the backpack! Force = Force, Impulse = Impulse YES/NO:____ EXPLANATION:   A fully dressed student with a backpack is at rest in the middle of a pond on perfectly frictionless ice and must go to shore. Can this be accomplished? Use KEY TERMS to explain:   Yes – throw the backpack! Force = Force, Impulse = Impulse Yes No Not enough info Not quite sure

HW – that was due today (workseet) Worksheet Texts open if needed 3 minutes to review with peers in the FRONT of the classroom Gossiping/ being off task will result in you going back to your seat and will guarantee the teacher will call on you. Then, we are rapidly popcorning!

QUESTIONS ABOUT… 24 or 26?

TWICE as much! m v = p 4 . 6 = 24 So…. 8 . 6 = 48 A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … a.… twice the mass and was moving at the same speed? TWICE as much! m v = p 4 . 6 = 24 So…. 8 . 6 = 48

TWICE as much! m v = p 4 . 6 = 24 So…. 4. 12= 48 A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … b.… the same mass and was moving with twice the speed? TWICE as much! m v = p 4 . 6 = 24 So…. 4. 12= 48

A bicycle has a momentum of 24 kg•m/s A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … c.… one-half the mass and was moving with twice the speed? Same! m v = p 4 . 6 = 24 So…. 2 . 12 = 24

A bicycle has a momentum of 24 kg•m/s A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … d.… the same mass and was moving with one-half the speed? HALF as much! m v = p 4 . 6 = 24 So…. 4. 3= 12

1.5 times as much! m v = p 4 . 6 = 24 So…. 12 . 3 = 36 A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … e.… three times the mass and was moving with one-half the speed? 1.5 times as much! m v = p 4 . 6 = 24 So…. 12 . 3 = 36

6 times as much! m v = p 4 . 6 = 24 So…. 12 . 12 = 144 A bicycle has a momentum of 24 kg•m/s. What momentum would the bicycle have if it had … f.… three times the mass and was moving with twice the speed? 6 times as much! m v = p 4 . 6 = 24 So…. 12 . 12 = 144

Recap Last class, we talked about impulse changing momentum. This class (and the next 2 classes), we are going to talk about what happens if that impulse occurs during 2 scenarios: When bouncing occurs When a collision occurs

POGIL from last class – 10 minutes Take out your notes from last class and go to the demo section. (Nerf Guns, Ping Pong Balls, Toppling) You will be shown the Nerf Gun and Toppling Demos, and you will get to try the Ping Pong Demos. BEFORE THAT…. I want you to consider the following question (write & answer in your notes) Would a head-on collision between two cars be more damaging to the occupants if the cars stuck together or if the cars rebounded (bounced) upon collision? (Assume the time of the collision is the same.)

Doesn’t matter either way Not sure! Would a head-on collision between two cars be more damaging to the occupants if the cars stuck together or if the cars rebounded (bounced) upon collision? (Assume the time of the collision is the same.) When the cars stick When the cars bounce Doesn’t matter either way Not sure!

POGIL from last class Cross out pages 3 – 4 … look like this: unless you want to challenge yourself to try what the Geo kids are doing…then, feel free to try them at home and check! 

POGIL from last class – 10 minutes You will be shown the Nerf Gun and Toppling Demos, and you will get to try the Ping Pong Demos. Then, working in the FRONT of the classroom, you MUST answer all questions A through F Please review your HW on the POGIL (page 2) Ensure that EVERYONE understands not only WHAT the solutions are, but WHY they are what they are…you should be able to transfer your thought process to other questions regarding similar concepts. ***NOT SURE/ QUESTIONS? ASK A TEACHER!!!*** Finish part G – Conclusion. 10 minutes to complete!

When is impulse larger? (heads down hands up) When objects bounce When objects don’t bounce Doesn’t matter either way Not sure!

Bouncing Ft = ∆(mv) Impulses are greater when bouncing takes place Falling flower pot hits your head Momentum stops Falling flower pot hits your head and bounces off Momentum is reversed. **Impulse to stop < impulse to “throw it back again”** 2(∆mv) Karate chop Pelton wheel 23

Just like the medicine ball exercise!!! Bouncing Think about a bouncing ball: Before it hits the ground: Speed = v Momentum = mv At the moment it hits the ground: Speed = 0 Momentum = 0 After it leaves the ground: Impulse needed to stop the ball = mv Total Impulse = 2mv Impulse needed to accelerate the ball upwoard = mv Important point: It only takes an impulse of mv to stop the ball. It takes twice the impulse (2mv) to make it bounce) Just like the medicine ball exercise!!!

If the time of impact is long, the force will be milder 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 for BOUNCE is REBOUND

A 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 the rebound effect, the greater the…

A rebound is a special type of collision involving: a direction change which results in a velocity change. Observe that the greater the rebound effect, the greater the… acceleration, 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 the rebound effect, the greater the… acceleration, momentum change, and impulse. The result of the direction change is a large velocity change.

HW – that was due last class #11-13, p. 100 Texts open if needed 3 minutes to review with peers in the FRONT of the classroom Gossiping/ being off task will result in you going back to your seat and will guarantee the teacher will call on you. Then, we are rapidly popcorning!

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 time…force x time = impulse!

HW – that was due last class 11b) 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 time…force x time = impulse!

HW – that was due last class 11c) 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 time…force x time = impulse!

HW – that was due last class 11d) Visualize yourself on a skateboard. In which of the scenarios do you experience the largest impulse? Catch Throw Catch an throw Same in all Catch and throw – it’s like bouncing! More velocity change, so more momentum change, so more impulse!

HW – that was due last class 12) Why is more impulse delivered when bouncing occurs? More velocity change, so more momentum change, so more impulse!

Go to your test seats… Open notes quest on Ch. 7 on Jan. 23 Normal quiz procedures apply Open notes, not open books No calc needed… cell phones OUT and SILENT When done, quiz in basket upside down and you may continue working on your HW (make your hypotheses and try them) Open notes quest on Ch. 7 on Jan. 23

HW – that was due last class 13) Why is the Pelton wheel an improvement over a wheel with flat blades?

Go to your test seats… And “Midterm Information” Normal quiz procedures apply Open notes, not open books No calc needed… cell phones OUT and SILENT When done, quiz in basket upside down and take a copy of your: “Momentum Conceptual review” (HW) Start working on this – it is HW!!! And “Midterm Information” Read the “Midterm Information” sheet tonight – we will answer any questions about it next class