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Math Help - Calculating speed.

  1. #1
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    Calculating speed.

    I currently have a machine that can calculate the time it takes for an object to travel one meter. (two lasers first one starts a timer second one stops it, The lasers are positioned exactly 1 meter apart.)

    So if an object was going 10 M/s (Meters per second) it would take 0.1 of a second (10 nanoseconds) to travel one meter. If it was going 1 meter per second it would take 1 second, obviously.

    What would the equation needed to turn the time taken into the speed (In Meters per second preferably)


    For those interested the program used is called Algodoo
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  2. #2
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    Quote Originally Posted by Mystery View Post
    I currently have a machine that can calculate the time it takes for an object to travel one meter. (two lasers first one starts a timer second one stops it, The lasers are positioned exactly 1 meter apart.)

    So if an object was going 10 M/s (Meters per second) it would take 0.1 of a second (10 nanoseconds) to travel one meter. If it was going 1 meter per second it would take 1 second, obviously.

    What would the equation needed to turn the time taken into the speed (In Meters per second preferably)


    For those interested the program used is called Algodoo
    v = \frac{\Delta x}{\Delta t}

    also ...

    0.1 sec does not equal 10 nanoseconds.

    10 nanoseconds = 10^{-8} sec

    0.1 sec = 100 milliseconds
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  3. #3
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    So basically Velocity is the Distance Divided by the time taken.
    thanks.
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  4. #4
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    However, it doesn't matter in this particular problem, because the laser travels one straight path. But generally in these problems you want the average speed. The formula v = \frac{\Delta x}{\Delta t} gives you the "average velocity" of the object, \Delta x is the object's displacement (change in position given by \Delta x = x_f - x_i). So the formula is not always the same thing as \frac{d}{\Delta t} which gives you the "average speed"! Because in the latter formula, "d" means the total distance traveled which isn't always the same as displacement.
    Here's an example: If a runner runs a distance d of 10 km and yet ends up at his starting point, his displacement is zero, so his average velocity is zero! But his speed is clearly NOT zero!
    Last edited by Roam; February 12th 2010 at 04:42 PM. Reason: typo
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