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3.3 Energy and Work: Why Air Bags?

3.3 Energy and Work: Why Air Bags?. December 10, 2013 Homework: 1-6,8 Honors add #9 Due Friday. DO NOW: Set up notebook Title/LO/SC WDYS?/WDYT? pg 277 Agenda Do Now Investigate. Learning Objectives Relate the work-energy theorem to safety. Success Criteria

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3.3 Energy and Work: Why Air Bags?

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  1. 3.3 Energy and Work: Why Air Bags?

  2. December 10, 2013Homework: 1-6,8 Honors add #9Due Friday • DO NOW: • Set up notebook • Title/LO/SC • WDYS?/WDYT? pg 277 • Agenda • Do Now • Investigate • Learning Objectives • Relate the work-energy theorem to safety. • Success Criteria • Explain how air bags keep you safe during an accident. • Describe how stopping distance affects force during a collision.

  3. Investigate 3.3 • 1.Question: How does stopping distance affect force during a collision? • Read entire investigate • 2.Set up data table • 3.Follow instructions step-by-step 1-7a • 4.Answer #5,6, and 7 under your data table in your notebook

  4. December 11/12, 2013 • DO NOW: • Leave space to answer 8a of the investigate. • Describe how a vehicles stopping distance affects force during a collision? • Agenda • Do Now • Physics Talk • Learning Objectives • Relate the work-energy theorem to safety. • Success Criteria • Explain how air bags keep you safe during an accident. • Describe how stopping distance affects force during a collision.

  5. 3.3 Physics Talk • A person’s head • The steering wheel or windshield • Air bag • What did the egg represent? • What did the table represent? • What did the rice represent?

  6. Physics Talk Continued • 1. The egg was held at a specific height in which it had max GPE. • 2.The egg was dropped in which the GPE gradually transferred into KE • 3. Work was done to stop the egg which changed the eggs KE. • The total work done on the egg is equal to the change in KE • Model the conservation of energy that occurred with the egg drop.

  7. Physics Talk Continued • Energy of motion KE=1/2mv2 • Same • Same • What is Kinetic energy and the equation? • Compare both of the eggs mass? • Compare both of the eggs velocities before impact?

  8. Physics Talk Contiued • The KE of the eggs were the same, but the KE changed much more quickly during the hard surface collision than with the soft surface collision. • So, how did the KE of the eggs change when it collided with the hard vs. soft surfaces?

  9. Investigate 8a

  10. Physics Talk Continued • WORK!! • W=Fxd • Units are in Joules (J) They are equal !(law of conservation of energy) WORK-ENERGY THEOREM W=△KE △ means “change in” • What do we call a force applied over a certain distance? • What is the relationship between work and the change in KE used to stop the egg?

  11. Physics Talk Continued • The surface had to apply a force over some distance? • The softer surface had a longer stopping distance due to the indentation seen in the rice vs. the harder surface where you could not see an indentation • How was the egg stopped? • Compare the stopping distances of the egg on the hard surface vs the softer surface.

  12. Physics Talk Continued • Getting rid of the KE a car and its occupants have before a collision • This can be done safely or dangerously (cause injury) • Energy Management

  13. Physics Talk Continued • Hard surface=short stopping distance=greater force to the egg (cracked) • Softer surface=longer stopping distance=less force to the egg (no crack) • Compare the force needed to stop the eggs with the stopping distance of the two different surfaces. • Refer to table on page 281

  14. Sample Problem on page 286

  15. Exit ticket • Explain how air bags keep you safe using the work-energy theorem.

  16. December 13, 2013Homework: Study for Finals ch 2-3.3 • DO NOW: • WDYTN pg 288 • Agenda • Do Now • Essential questions • Review PTG • Quiz • Go over ch 2 exam • Learning Objectives • Relate the work-energy theorem to safety. • Success Criteria • Explain how air bags keep you safe during an accident. • Describe how stopping distance affects force during a collision.

  17. Essential Questions: • Explain how two different forces can cause the same change in kinetic energy of an object. Include the definition of work in your explanation. • How did you test whether a material is good for cushioning an egg during a collision?

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