SOLUTION: The text asks us to solve the following statements using either the "object dropped" or "object thrown" formulas. Given formulas: Object dropped {{{h=-16t^2+s}}} Object thrown

Question 192033: The text asks us to solve the following statements using either the "object dropped" or "object thrown" formulas.
Given formulas:
Object dropped
Object thrown
h=height (ft)
s=initial height (ft)
t=time in motion
v=initial velocity (feet/second)
The statement:
An acorn falls 45 feet from the top of the tree.
This is what I have tried:
The acorn falls so I used the "object dropped formula". The height (feet) that the acorn fell was 45 feet and the initial height of the acorn was 45 feet. This is how I wrote that out:

Then I attempted to solve for 't'.
I subtracted 45 from both sides ending up with:

I noticed right away that in order to make this true 't' had to be 0. But if t=0 then that means it took the acorn 0 seconds to fall down from the top of the tree. Impossible right???
What am I doing wrong? Please help.

Found 2 solutions by stanbon, Earlsdon:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The acorn falls so I used the "object dropped formula". The height (feet) that the acorn fell was 45 feet and the initial height of the acorn was 45 feet. This is how I wrote that out:

Then I attempted to solve for 't'.
I subtracted 45 from both sides ending up with:

I noticed right away that in order to make this true 't' had to be 0. But if t=0 then that means it took the acorn 0 seconds to fall down from the top of the tree. Impossible right???
What am I doing wrong? Please help.
-------------
You probably want to find the time it takes for the object
to reach the ground which means it has zero height.
-16t^2 + 45 = 0
-16t^2 = -45
t^2 = 45/16
Positive solution:
t = sqrt(45/16)
t = (3/4)sqrt(5) seconds
=============================
Cheers,
Stan H.

Answer by Earlsdon(6294) (Show Source): You can put this solution on YOUR website!
What you are trying to find is how long does it take the acorn to reach the ground where h = 0ft. (not h = 45ft., that's the initial height.), so...

secs.
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