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Day 3 – ImpulseMr. LambertIntegrated Science 1ATrimester 1, 2014

+ Bell RingerWhat are some of the factors that automobile designers and engineers must consider when designing a crumple zone as a safety feature?

Crumple zone – part of the body of a car thatcompresses during a collision

+Agenda

1. Bell Ringer

2. Lab Activity

3. Impulse videos

4. Worksheet

5. Exit Slip

+Learning Targets

On your Bell Ringer Sheet, write the following:

We will apply the concept of impulse in the analysis of collisions.

+ Lab ActivityEach group will be given a cart with a block on it.Your setup will be as shown in the image to the right. Instead of 10 cm, you will stack two textbooks.Your challenge: construct a crumple zone that cushions the collision of your car so that the wooden block does not flip over.You can use tape, paper, string, and rubber bands (if available).

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If the challenge is too easy, add 1 or 2 more textbooks to make the ramp steeper.If the challenge is too hard, remove 1 book.

+Answer questions in your notebook1. If you managed to complete the challenge and create a

good crumple zone, what designs made it effective?2. As you were trying different crumple zones, what designs

were not effective? Why?3. How do air bags keep us safe during collisions? Use the

concept of impulse to explain why.4. Explain why you bend your knees when you jump to the

ground.5. Helmets are designed to protect cyclists. How would the

designers of helmets make use of the concept of impulse to improve their effectiveness?

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http://youtu.be/yUpiV2I_IRI?t=7m37s

Impulse and Crumple Zones

Explain

+ Impulse Videos

Crash test

• https://www.youtube.com/watch?v=dkMCFcEkQ0w

Physics of Football

• https://www.youtube.com/watch?v=s6QR0KdyTFY

+ What is impulse?Impulse = Force x change in timeImpulse is the same for a collision (as long as the mass of the object and its velocity stay the same).A smaller time means a bigger forceA bigger time means a smaller forceCompare falling on concrete vs.

falling on grass or a bed

Demo: throwing foam ball vs lacrosse ball

+Egg throw demonstration

Time to go throw some eggs!https://www.youtube.com/watch?v=7RSUjxiZnME

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Our target is LARGE. If you miss the target, you will clean the egg, you will receive an immediate referral, and this activity will end for everyone.If you think you can’t hit the target, do not throw the egg.

WARNING! ACHTUNG!

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1. Impulse is the same for a collision (as long as the mass of the object and its velocity stay the same).

2. A smaller time means a bigger force3. A bigger time means a smaller force

4. In this activity, we will apply a force to a moving egg to bring it to a stop. The egg will be moving as fast as we can throw it!

5. Predict: Is it possible to stop an egg without breaking it? HOW?

Egg Throw

Explore

+Egg Throw: Free Body Diagram

Egg on the Wall

Egg on the Sheet

Force of the Wall

Force of the

SheetExplain

+Exit Slip

In cars built before 1970, dashboards were made of hard metal. Today, dashboards are padded. Why is it better to have a passenger hit a cushioned dashboard than a hard metal dashboard? Use the concept of impulse to answer this question.