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Help with this physics problem

  1. Sep 6, 2005 #1
    Hey just starting physics and i am lost. This is the problem:
    A car traveling 35 mi/h is to stop on a 35 meter long shoulder of the road. What minimum deceleration is required?

    If you could type out How you would this is would be GREATLY appreciated.

  2. jcsd
  3. Sep 6, 2005 #2
    okay well 1st of all convert mi/h to km/h because the stopping area is given in metres.

    The question essentially asks how rapidly must the car decelerate in order to reach a velocity of 0 over 35 metres.

    Well the average speed the car will have is 1/2 its initial velocity if we take decleration to be uniform. Therefore, using 1 mi = 1.5 k, the car will have an average speed of 26.25 km/h.

    This is equivalent to 437.5m/minute or 7.29166m/second.

    Therefore the car will cover the 35 metres in <5seconds.

    Therefore the car must decelerate at >7m/s to stop in time
  4. Sep 6, 2005 #3
    You might also find this formula to be very useful
    [tex]v_2^2 = v_1^2 + 2ad[/tex]
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