# Help- throwing apples

cherica48
Help me please I've been stuck on this problem for an hour now...

John throws and apple from a height of 1.3 m with velocity of 2.4 m/s. Will it reach his friend in a treehouse 5 m above the ground?

My book gives the answer "No, it will only reach 1.6 m," but I really want to know how to do this. Any help is greatly appreciated. Thanks!

Jeff Ford
I would think you'd need to know the angle of the throw and how far away the friend is, but I'm quite a beginner so I'm not sure.

Mentor
Consider conservation of energy. Will the apple have enough energy to make it to that height (regardless of the angle it's thrown)?

cherica48
Whoops, sorry about the homework help violation...in such a rush to figure this out that I didnt see the rule.

I'm pretty sure he wants us to use a Free Fall kinda thing, with an equation like Vf=Vi+2(a)(t), but not all those factors are there. This is basic physics stuff, we're studying like -9.81 acceleration for gravity, and how to find displacement and velocity and all that.

Mentor
If you threw the apple straight up at that speed, how high would it go?

cherica48
Doc Al said:
If you threw the apple straight up at that speed, how high would it go?

Well that's what the question is asking, and I assume that's displacement. Displacement in our book is

D= .5(Vi+Vf)t

I have Vi(2.4), and Wf would be 0 once it reached the top, but I don't know t. Am I using the wrong formula here? I have no idea what to do... Mentor
You can find the time using the definition of acceleration:
$$v_f = v_i + at$$