1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Acceleration of object - how much time does it take

  1. Jul 11, 2006 #1

    does anyone know how to calcuate the distance it would take for an object to reach 45mph starting from 0mph with a time limit of 3.7 seconds?

    its not a homework question, i acctually race go karts and was curious if there was a way to calculate that

    thanks for your help
  2. jcsd
  3. Jul 11, 2006 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    EDIT OOPS!!!!!! I was sure you had asked about the *acceleration*!
    Once you have the acceleration, you may calculate the distance using
    [tex] x_f = {1 \over 2} a_x t^2 [/tex]

    Of course. The acceleration is simply [itex] {v_{x,f} - v_{x,i} \over \Delta t } [/itex].

    You have to be careful with units. I am not sure what units people use quote acceleration of cars in the non-metric system, but it could be in mph/s (miles per hour per second) or miles per hour squared or miles per second squared. I have a hunch that the first would be the standard one (mph per second) in which case you would just divide 45 mph by 3.7 seconds. (In the metric system, it's of course given in m/s^2, meter per second squared).

    Last edited: Jul 11, 2006
  4. Jul 12, 2006 #3
    45 mph = 66 ft/s, use ft/s in the above formula.
    Therefore, acc. = 66 ft/s / 3.7 s = 17.84 ft/s^2 = a.

    So the distance, x, using the formula = 0.5 (17.84) (3.7)^2 = 122.1 feet.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook