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Find force on a crate while a driver accelerates

  1. Sep 24, 2012 #1
    1. The problem statement, all variables and given/known data
    A crate with a mass of 250 kg rests on the bed of a truck that is moving at a speed of 40.0 km/h. The driver accelerates to a speed of 70.0 km/h in 8 s. Assuming the force is constant, what force acts on the crate during this time? Assume that the crate does not slide on the bed of the truck.
    A) 18 N
    B) 3400 N
    C) 240 N
    D) 260 N


    2. Relevant equations

    f=ma

    3. The attempt at a solution
    Well I would think that you would find acceleration giving you 3.8m/s2 and then take 250/3.8 but that gets you 65.789 which is not an option.
     
  2. jcsd
  3. Sep 24, 2012 #2
    Make sure you're converting the km/h to m/s.
     
  4. Sep 24, 2012 #3
    That helped. Thanks!
     
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