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Homework Help: Equations of Velocity

  1. Feb 10, 2013 #1
    1. The problem statement, all variables and given/known data

    The speed, v, of an object is given by the equation v = At3 - Bt4 where t refers to time. What are the dimensions of A? (Express your answers using only m for distance and s for time.)

    2. Relevant equations

    3. The attempt at a solution

    I know the answer. A is m/s4 and B is m/s5
    I just do not know why that is. I want to have an understanding of why, rather then just knowing what to do.
    Thank you in advance.
  2. jcsd
  3. Feb 10, 2013 #2


    Staff: Mentor

    Okay you do know that velocity is m/s right?

    so looking at the first term a * t * t *t the t's provide s^3 so then the A must be m/s^4 when multiplied together three of the s's are cancelled out leaving A t^3 to be m/s

    You can do this symbolically like this:

    (m/s) = A (s^3) and dividing both sides by s^3 we get A = (m/s^4)

    similarly for (m/s) = B (s^4) hence B = (m/s^5)
  4. Feb 10, 2013 #3
    Oh i see! They just want m/s! Completely understand now. Thank you
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