Question

How long did it take to reach the bottom of the slope

Answer 1

To solve this we are going to use the kinematic equation for final velocity: $V_{f}=V_{i}+at$
where
$V_{f}$ is the final velocity
$V_{i}$ is the initial velocity 
$a$ is the acceleration 
$t$ is the time

We know for our problem that the the velocity at the beginning of the slope is  $2.0ms^{-1}$, so $V_{i}=2.0$. We also know that the speed ad the bottom of the slope is $20ms^{-1}$, so $V_{f}=20$. We also know that the acceleration is $6ms^{-2}$, so $a=6$. Lets replace those values in our formula and solve for $t$:
$V_{f}=V_{i}+at$
$20=2+6t$
$6t=18$
$t= \frac{18}{3}$
$t=3$ seconds

We can conclude that it takes the roller coaster 3 seconds to reach the bottom of the slope.