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Homework Help: Finding the spring constant of a accident safety system

  1. Jan 26, 2010 #1
    1. The problem statement, all variables and given/known data
    An accident safety system uses a spring to absorb the energy of a car before the car collides with a bridge abutment.
    The vehicle has a mass of 1000kg and the design calls for stopping a car moving at 5m/sec (11.2 mi/hr) in 0.5m.
    Find the spring constant k

    2. Relevant equations
    F=kx -> k=F/x

    3. The attempt at a solution
    I am having trouble finding the force of the collision. It is needed to find k, is it not? I was thinking I may need to use a kinematics equation to do this and solve for the acceleration (deceleration in this case).
  2. jcsd
  3. Jan 26, 2010 #2
    I tried using the equation:
    and solved for a, resulting in a=25m/s^2
    Is this correct?
  4. Jan 26, 2010 #3
    Shouldn't the acceleration be negative?
  5. Jan 26, 2010 #4


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    Science Advisor
    Homework Helper

    Nice work, Revan718. Acceleration is negative.
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