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Momentum and Impulse

Understand momentum as mass multiplied by velocity and impulse as change in momentum

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It's Not the Crash It's the Sudden Stop

It?s Not the Crash, It?s the Sudden Stop

Credit: Simon Yeo
Source: http://www.flickr.com/photos/smjb/8107539280/
License: CC BY-NC 3.0

The image seen above shows a crash test dummy ready to help scientists and engineers study the effects of motor vehicle collisions on the human body. By implanting a combination of sensors and life like structures to model human bones, investigators are able to better understand the effects of impact in order to design safer, more efficient vehicles.

Amazing But True!

Credit: Arup Malakar
Source: http://www.flickr.com/photos/87135065@N00/8111802805
License: CC BY-NC 3.0

Seatbelts prevent us from flying forward when the car stops abruptly [Figure2]

  • The tendency for an object to resist a change in acceleration is known as inertia.
  • The videos of the crash test dummies in action show that without a seatbelt and/or an air bag, the crash test dummy would continue to move forward until acted upon by an external force.
  • When you accelerate in a moving vehicle, the pressure you feel on your back from the seat is felt because the car is moving but your body is initially sitting still.

Show What You've Learned

Using the information provided above, answer the following questions.

  1. When you come to a sudden stop while driving a car, why do you feel the seat belt pressing on your chest?
  2. Since seatbelts simply act as a method to reduce your velocity, why do they need to be used? What is wrong with the assumption that the steering wheel or the dash of the motor vehicle would bring you to a safe stop, similar to the seatbelt?
  3. If the injuries in a car crash are a result in the sudden stop or change in velocity, what could be done to make automobile crashes safer?

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Image Attributions

  1. [1]^ Credit: Simon Yeo; Source: http://www.flickr.com/photos/smjb/8107539280/; License: CC BY-NC 3.0
  2. [2]^ Credit: Arup Malakar; Source: http://www.flickr.com/photos/87135065@N00/8111802805; License: CC BY-NC 3.0

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