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Velocity - time home work check

  1. Mar 22, 2012 #1
    1. The problem statement, all variables and given/known data

    A car accelerates from 0 to 30m s ^-1 in 5.0 seconds, travels at a constant 30m s^-1 for 15.0 seconds and then brakes to a stop in 10.0 seconds.

    1) calcualte the acceleration (assumed constant) in each section of the motion.
    2) calculate distance travelled
    3) what is 30m s^-1 in km/h?

    2. Relevant equations

    a= change in velocity / change in time
    d(t) = v_0 x t + (a/2)t^2


    3. The attempt at a solution

    a=(30-0)/5 = 6 m/s
    d(t) = 0 x 5 +(6/2_ x 5^2 = 75m

    a=(30-30)/15 = 0 m/s^2
    d(t) = 30 x 15 + (0/2) x 15^2 = 450m

    a=(0-30)/10 = -3m/s^2
    d(t) = 30 x 10 + (-3/2) x 10^2 = 150m
     
  2. jcsd
  3. Mar 22, 2012 #2

    PhanthomJay

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    Looks OK!
     
  4. Mar 22, 2012 #3
    Thanks so much! I'm working so slowly trying to get it right. Thanks again, the feedback is a boost!
     
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