## Homework Statement

Suppose that an object is thrown into the air with an initial upward velocity of Vo meters per second from a height of ho meters above the ground.

## Homework Equations

Then, t seconds later, its height (h(t) meters above the ground is modeled by the function h(t) = -4.9t^2 + Vot + ho.

## The Attempt at a Solution

a) Find its height above the ground t seconds later.

I got h(t) = -4.9t^2 + 14t + 30, and I checked the back of the book and it is correct.

b) When will the stone reach its highest elevation?

I tried a lot of things like plugging in various h's and t's, and using the quadratic formula, but I did not have much success.

c) When will the stone hit the ground?

Same as b), I wasn't sure where to start, but I made some educated guesses, however they proved wrong.

NOTE: I have all of the correct answers. I am not asking for anyone to do my homework for me or give me the answers. I would just like to be guided in the right direction so I will never have to ask for help on these types of problems again. I have worked for 20 minutes straight on this problem, and I know for a fact it shouldn't take that long.

rock.freak667
Homework Helper
Well if $$h(t) = -4.9t^2 + 14t + 30$$ doesn't this represent a parabolic curve? doesnt this curve have a maximum point...which would correspond to the max height and the time it occurs

Yes.

How do you find the maximum value of the parabolic curve, though?

rock.freak667
Homework Helper
Find the the first derivative and equate to zero and solve for t

Find the the first derivative and equate to zero and solve for t

Would you mind clarifying what you mean by "the first derivative?" I don't quite understand what you mean. Thanks.

HallsofIvy