physics assignment?

Question

4. ) Ball A is dropped from the top of a building at the same instant ball B is thrown vertically upward from the ground. When the balls collide, they are moving in opposite directions, and the speed of A is twice the speed of B. At what fraction of the height of the building does collision occur?

Answer 1

Hmm.. interesting

I would start with basic equations

Va=gt
Vb=V0-gt

Ha=0.5 g t^2
Hb=V0t - 0.5 g t^2
and
H = Ha + Hb (the total height of the building)

Since when the meet Va=2Vb
From the first set we have

gt=2(V0 - gt) so
V0= 3gt/2

Since it is the fraction they want than a fraction they will get!

F=Hb/(Ha+Hb)=?

F= (Vo t-0.5 g t^2)/( V0t - 0.5 g t^2 + 0.5 g t^2)
F=(Vo t - 0.5 g t^2)/((Vo t)
F=1 - g t/(2 V0)

now since V0=3gt/2

F=1 - gt/ [2 (3gt/2)]

F= 1- 1/3= 2/3

Answer 2

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Answer 3

http://answers.yahoo.com/question/index;_ylt=AqWZLUt7oa8Ulp2S_RasvOMjzKIX?qid=20070705191754AAUvAm8

maybe check out this guy, he might be in the same class as you