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Help determine impact speed

  1. May 9, 2015 #1
    I know an exact answer is impossible but an estimate will prove the following statement impossible. Allstates insured driver said he backed up hit my sons motorcycle, did not feel the impact, and stopped when he heard it hit the ground. He parked and got out and the motorcycle was 3' from the rear bumper of the truck.
    What speed would the 6025lb truck have to be going to knock the 550lb motorcycle 3' beyond the bumper of the truck. I know he would have to be traveling at a rate of speed much higher than he was and I'm looking for numbers to prove it to the insurance company.
    My belief on what happened. If he was backing up at 5mph then he is traveling 7.3" per second. It takes a 36" object .43 seconds to fall (without the impact). He didn't stop until he heard the impact which means he would have traveled 3.1' before he stopped. His rear tire is 30" from his bumper proving his rear tire would have ran onto the rear tire of the motorcycle. Does this make sense?
    Sorry I'm not a physicist or mathematician just an elementary teacher trying to fight the insurance company to cover the damages to my sons motorcycle.
    Any help is greatly appreciated.
    Last edited by a moderator: May 9, 2015
  2. jcsd
  3. May 9, 2015 #2


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    2017 Award

    Staff: Mentor

    Please don't post email addresses here.

    That question is impossible to answer without a detailed analysis. There are experts for this, and the insurance won't take "someone on the internet said this!" seriously.

    Some points to think about:
    - real-life impacts are not collisions between point-like or spherical objects
    - reaction times of drivers are variable
    - motorcycles are not falling down vertically. If they start close to the balanced position, they can need a long time to hit the road with the side.
    - after hitting the road, motorbikes can still move
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