Question

A ball rolls down an inclined plane such that the distance (in centimeters) that it rolls in t seconds is given by s(t) = 2t^3 + 3t^2 + 4 for 0<=t<=3

At what time is the velocity 30cm/s?

Answer 1

I've got the first part figured out (velocity at t = 2), but using the same equation I used for the previous problem doesn't work, dimbeni.

Answer 2

v(t)=6t^2+6t
2t^3+3t^2+4=30 -> 2t^3+3t^2-26=0

Answer 3

Yup. I got (-1 + sqrt(24)) / 2 as the answer but it doesn't seem right.

Answer 4

Ok, sorry. I was mistaken.
It's v(t)=30.
Then t^2+t-5=0
I get (-1+sqrt(21))/2

Answer 5

So I'm right? Sweet...!

Answer 6

Good answer yet again! Thanks dimbeni...:D