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Homework Help: What average force is it brought to rest?

  1. Nov 17, 2007 #1
    1. The problem statement, all variables and given/known data

    Auto companies frequently test the safety of automobiles by putting them through crash tests to observe the integrity of the passenger compartment. If a 1000. kg car is sent toward a cement wall with a speed of 14 m/s and the impact brings it to a stop in 8.00 * 10^-2 seconds, with what average force is it brought to rest?

    2. Relevant equations

    F = mv/t

    3. The attempt at a solution

    F = mv/t = (1000*14)/(8e-2) = 175000 N
  2. jcsd
  3. Nov 17, 2007 #2


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    Homework Helper

    There you have it! The average acceleration during the simulated crash is the change in velocity (14 - 0 m/sec) divided by the time interval over which it occurred (0.08 sec) or 175 m/(sec^2) , which is almost 18 times the acceleration of gravity. The average force on the car is then its mass times that average acceleration or

    175 m/(sec^2) ยท 1000 kg = 175,000 N (or almost 18 times the car's weight).
  4. Nov 18, 2007 #3
    Thats right.
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