Posted by **Oscar Zambrano** on Thursday, November 3, 2011 at 7:33am.

a stone is dropped from a 75m building. when a stone has dropped 15m, a second stone was thrown downward with an initial velocity such that the two stones hit the ground at the same time. what was the initial velocity of the second stone.

- Physics -
**Henr =y**, Friday, November 4, 2011 at 11:08pm
d = Vo*t + 4.9t^2 = 15,

0 + 4.9t^2 = 15,

t^2 = 3.06,

t = 1.75s. = Time to fall 15m.

Therefore, the 1st stone had a 1.75s

headstart:

d1 = 0 + 4.9t^2 = 75

t^2 = 15.31,

t1 = 3.91s.

t2 = 3.91 - 1.75 = 2.16s.

d2 = Vo*t + 4.9t^2 = 75,

2.16*Vo + 4.9(2.16)^2 = 75,

2.16Vo + 22.9 = 75,

2.16*Vo = 75 - 22.9 = 52.1,

Vo = 24.1m/s. = Initial velocity of 2nd stone

- Physics -
**Henry**, Friday, November 4, 2011 at 11:15pm
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