Advanced/Notes 7.3
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Transcript of Advanced/Notes 7.3
Collisions and ImpulseSection 7.3
Collisions and Impulse
• How do measure an impulse?
Collisions
• Large forces occur during collisions
• These forces deform objects
• Deformation occurs because huge jumps in forces happen over a short amount of time
Collisions
• Time of collisions is very short
• We need not worry about the exact time dependence of the force
• We can use average force
Impulse
• Term for the change in forces and the amount of time it takes is impulse
• Impulse =
• Unit = N·s
Impulse
• Can have the same change in momentum
• A large force acting for a short time
• A small force acting for a longer time
• Bend your knees when you land
Why does it matter?
• http://www.youtube.com/watch?v=C08JBiq2eJ4
• If I drop an egg…
Why airbags?
• Driving along, suddenly a brick wall appears in front of you and you crash. Your mass is 60 kg and you were driving 25 m/s. With no airbag, your body comes to rest in 3 x 10-4 s. An airbag can extend the time to rest by a factor of 100. Calculate the two impulses.
Homework
• Read Section 7.3• Do Problems # 15 – 19, Page 188• Bonus # 21• Egg Drop Challenge