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Homework Help: Need help with an inelastic collision problem

  1. Nov 29, 2003 #1
    A car weighing 900 kg is waiting at a stop sign. A car weighing 1200 kg hits the oter car. The cars move .76 m after the collision. The coefficient of friction between the sliding tires and the pavement is .92. I need to find the speed of the car right before the collision.
    I dont know what to use. Conservation of momentum doesnt work because I need at least one of the velocities.
  2. jcsd
  3. Nov 30, 2003 #2
    I think conservation of momentum is the right idea. I think you got to use it.
    You got to find the final momentum. The idea is that the cars stick together after collision. So the final momentum is [itex](m_1 + m_2)v_{final}[/itex]. You got to find [itex]v_{final}[/itex].
    You can do that. The cars are decelerated by a constant force of friction. This force is [itex]F = .92(m_1 + m_2)g[/itex]. From [itex]F[/itex] and [itex]d = .76m[/itex] you can calculate [itex]v_{final}[/itex].
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