Acceleration is the rate of change of the velocity per unit time.

We are given that the velocity changes from 0mph to 60mph in 15 seconds. To find the average rate of change, take the difference in the velocities divided by the difference in time.

(`Delta v` is the change in velocity and `Delta t` is the change in time.)

`"Acceleration"=(Delta v)/(Delta t)=(60-0)/(15-0)=(4"mph")/("sec")`

We have a unit of time in the numerator and denominator (hours and seconds) so we can rewrite this in other units. In the U.S. we still frequently use the imperial system of measurements and acceleration is reported in `"ft"/"sec"^2` .

`4"mph"=(4"m")/"h"=(4"mi")/"h"*"h"/(3600"s")*(5280"ft")/"mi"=5.8bar(6)"ft"/"s"`

So `(4"mph")/s=5.8bar(6)"ft"/"s"^2`

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The SI unit for acceleration is `"m"/"s"^2` . 1ft=.3048m so:

`5.8bar(6)"ft"/"s"^2=5.8bar(6)*.3048 "m"/"s"^2=1.78816 "m"/"s"^2`