Question

A high school athlete runs `1.00 * 10^2` `m` in `12.20` `s`. What is the velocity in `m``/``s` and `km``/``h`?

Answer 1

`8.20ms^-1` (3sf) and `29.5kmh^-1` (3sf)

Explanation:

In order to calculate the velocity we need both the distance travelled and the time taken to travel that distance. In this case we have both, I will start by converting the `1.00` x `10^2` into standard form which is `100`m

So `v = d/t`

`d = 100m` & `t = 12.20s`

Substitute both these values into the equation:

`v = d/t = (100m)/(12.20s) = 8.20ms^-1`

I like to keep the units in the calculation to make working the units of velocity out easier.

Now we know the velocity in `ms^-1`. To calculate the speed in `kmh^-1` we need to convert both the `m` & `s`, this can be done in multiple ways. However we know that `1000m` = `1km` and `1`hour = `3600`seconds.

Therefore we need to multiply our answer by: `(1000m)/(3600s)` So...

`v = 8.20ms^-1` x`3.6 = 29.5kmh^-1`

Note: I retained the non-rounded value in the calculator through the calculations, this will improve your accuracy and avoid rounding error.