# You run a 100-yd dash in 9.8 seconds. What is your speed in miles per hour?

Nov 13, 2015

20.90 mph

#### Explanation:

This is a problem that is employing conversion and conversion factors.

we'er given a yards per second speed, so need to convert yards to miles and seconds into hours.

$\frac{100 y}{1}$ x (5.68E^-4m)/(1 y)$=$.0568 m

then we convert the seconds into hours

$\left(9.8 s\right)$ x (1m)/(60 s) $x$ (1 h)/(60 m)$=$.0027 hr

Now that you have the right units, you can use the speed equation

$S = \frac{D}{T}$ = $\frac{.0568}{.0027}$ =$20.90 m p h$

It's important to note that when I did this calculations I did not round. Therefore, if you were to calculate $\frac{.0568}{.0027}$ your answer would be slightly different due to rounding errors.