[111] Throw-up problem - Launch/freefall

[WPCareyDevil]

Homework Statement

A stone is launched straight up by a slingshot. Its initial speed is 19.8 m/s and the stone is 1.40 m above the ground when launched. Assume g = 9.80 m/s2.
(a) How high above the ground does the stone rise?
wrong check mark m
(b) How much time elapses before the stone hits the ground?

Homework Equations

D= Vot + (1/2)at^2
V=at+Vo

The Attempt at a Solution

Vi=19.8m/s
d=1.4m
a=-9.8m/s

I actually solved another question I had while typing it up on here.. maybe this one will be the same.

Ok, I've attacked this thing every way I can think of, and my problem is the integration of it being launched from 1.4m above the ground. I tried 1.4=19.8t+ (1/2)(-9.8)t^2, solving quadratically for t=3.9688 and t=.071987, neither of which are correct. I know finding the time is the key to the solution, but I am not sure how to integrate the 1.4m into the formula.

Can someone point me in the right direction?

 

[BuGzlToOnl]

Let me rewrite this your formula for part A is y= (v^2-v0^2)/(2a).

After you get your y component your formula for Par B is: t= v-v0/a.

t = time
a = acceleration
y = distance (vertical)

And that should give you the answer for the problem.

Sorry went through 3 or so edits kept copying the wrong equation, that should be it thou. Times the answer by 2 to get the up time and downtime for Part B.