Difficult# When Acceleration is Not Constant: Skateboarder

CLMECH-JKVE6O

A skateboarder rolling down a curved ramp will experience an acceleration that is not constant. Lets suppose we can approximate her acceleration as:

$$a(t) = a_o-bt\:,$$

...where $a_o=5.00\;m/s^2$ and $b =3.33\;m/s^3$, as shown below.

Assuming her initial velocity was zero at $t=0$, what is her velocity at the bottom of the ramp (i.e. at time $t = 1.50\;s$)?