Velocity and position
If s(t) = (1/3)(t^3) - (3/2)(t^2) - 18t
During what time is the object moving towards the origin?
I know I set s(t)v(t) < 0, but from there on Iím a little stuck.
When the velocity is 10m/s, find its displacement.
My answers to this were : -511/6, and 208/3
Is this correct?
How many times does the object cross a marker on the line located at s = 20?
Iím not sure how to do this one.
Any help is appreciated.
so for the last question where i have to find how many times the object crosses s=20
i set s(t) = 20, giving me 20 = (1/3)(t^3) - (3/2)(t^2) - 18t
after bringing the 20 over and finding the lowest common denominator, i get
2t^3 - 9t^2 -108t -120 = 0
i tried using the factor theorem, but nothing seems to work out.
Are you allowed to draw a graph to answer the question ....? If so, it's clear that there's only one value of t greater than zero.
Originally Posted by Shapeshift