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Homework Help: Finding constant velocity,final velocity and acceleration of these cars?

  1. Oct 26, 2011 #1
    1. The problem statement, all variables and given/known data
    Two cars go the same distance in a straight line. Car A covers the distance at a constant velocity. Car B starts from rest and maintains a constant acceleration. Both cars cover a distance of 517 m in 215 and are moving in the + direction. Whats the constant velocity of car A as well as the final velocity and acceleration of car B?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Oct 27, 2011 #2


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    Did you by any chance mean 21 s [seconds] rather than 215 and no units.
  4. Oct 27, 2011 #3
    @ PeterO "Did you by any chance mean 21 s [seconds] rather than 215 and no units."
    Yes I did.Thank you for pointing that out.It's supoose to be 21 seconds not vaugely 215.Also if it helps I know for sure that the constant velocity of Car A is 2.40 m/s.
    Last edited: Oct 27, 2011
  5. Oct 27, 2011 #4


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    I hope you really meant 24.6 for the constant velocity.

    One of the useful formulae for motion under constant acceleration is

    s = (u + v)/2 .t

    s = displacement, u = initial velocity, v = final velocity, t = time.

    for acceleration zero, u = v so the (u + v)/2 = (v + v)/2 = v

    The formula becomes s = vt, which you use to get that 24.6

    when an object starts from rest, u = zero, so the formula becomes s = v/2 . t

    from that you can get the final velocity.

    as for acceleration .. the car reaches that velocity in 21 seconds, so you can divide by 21 to find the acceleration.
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