Calculus based kinematics problem.

[Phlebas]

Homework Statement

A trolley is released from rest from the top of a runway which is 8m long. The displacement, s in metres, of the trolley is given by the expression(see below) where t is in seconds. Using calculus initially determine (a) an expression for the velocity of the trolley (b) the acceleration of the trolley (c) the time it takes the trolley to reach the bottom of the runway (d) the velocity of the trolley at the bottom of the runway.

Homework Equations

s=2t+t²

The Attempt at a Solution

So I differentiated the displacement expression once to get a velocity expression and twice to get an acceleration expression. Can't quite figure out how to do (c) or (d) though, as my calculus is pretty rusty.

 

[TaxOnFear]

You have an expression for displacement in terms of t (time). You know the length of the runway, therefore you can find the time it takes to travel down said runway, yes?

 

[Phlebas]

slip of the brain. I get it now.