To measure the height of a tree, you throw a rock directly upward, with a speed just fast enough that the rock brushes against the uppermost leaves and then falls back to the ground. If the rock is in the air for 3.6 s, how tall is the tree?

Question

anonymous · Answer

That's some precision you got there :D 

ok.. so the rocks in air for 3.6 s.. can u calculate how high the rock went?

anonymous · Answer

Im not sure which formula to use

anonymous · Answer

you just have three equations.. 
U know that the initial position of the rock is same as its final position (as it returns).. so that gives u the displacement yea?
yu knw the acceleration huh?
also time is given..

anonymous · Answer

$$x=X _{0}+ V _{0} t=(1/2)(a)(t)^{2}$$

anonymous · Answer

that second equal sign is meant to be a + sign

anonymous · Answer

yea.. great.. using that equation.. u can find the initial speed..  Vo

anonymous · Answer

ok