# Thread:

1. ## 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

2. Originally Posted by Mystery
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

3. So basically Velocity is the Distance Divided by the time taken.
thanks.

4. 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!
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