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Homework Help: Road Physics

  1. Nov 23, 2009 #1
    1. The problem statement, all variables and given/known data
    What impact does physics facts like momentum, friction, collision, forces, inertia and second collision have on race driver crashes.
    Particular race: The Lexmark Indy.
    Particular year: None

    2. Relevant equations

    3. The attempt at a solution
    I can't seem to find a good crash and thats why I require assistance.
  2. jcsd
  3. Nov 23, 2009 #2
    In high speed collisions, Inertia can often be fatal.

    Inertia is an objects reluctance to change direction or alter it's motion. So it has direct connotations with Momentum. If you are moving in a care at 120mph, you are also moving at 120mph as observed by someone in an inertial frame of reference. In a crash, both the car AND you need to be stop. The car is totalled due to it's design (crumple zones and such), but you (a fleshy construct) will not be stopped until ALL of your momentum has been transferred. Your high inertia which is dependent on your mass and the speed at which you are moving will make this difficult and painful.

    Now transfer of momentum requires a force. To get rid of your momentum a change in momentum (which is a force must be induced). So without a seatbelt you would crash into the windscreen, and due to Newton's 3rd Law, the windscreen would induce an equal and opposite force back on you. So you would be crushed to death.

    It gets messy with the explanations when you start considering Kinetic energy also.
  4. Nov 23, 2009 #3
    Thankyou, that makes sense :) but is friction like Inertia?
  5. Nov 23, 2009 #4
    Friction is like inertia in that you need to overcome a higher resistance when changing or beginning acceleration, then after the object is in motion less force is required to keep it in.
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