Question

The position function of a particle is given by s(t) = t^{3}-3t^{2}-7t, t\ge 0 where s is measured in meters and t in seconds.
When does the particle reach a velocity of 20 m/s?

PLEASE HELP. I found the derivative which is 3t^2-6t-7. Now do I set that equal to 20 or do I try to put 20 in for t?

Answer 1

You want v=20, so, just solve

3t^2-6t-7 = 20

If you put in t=20, that will give you the velocity after 20 seconds. C'mon - think about what the variables mean...