A simple problem but i cant seem to get the answer i am told. I am thinking that i have mixed up my equations of motion(adsbygoogle = window.adsbygoogle || []).push({});

The question i have to answer is this.

A boy throws 2 stones verticly downward from a 50meter high cliff inot a calm pool of water.The 2 stones are thrown 1 second apart and the first stones initial velocity is 2m/s downwards. The 2 stones are seen to have hit the water at the same time.

a, How long after the release of the first stone do the 2 stones hit the water?

b, what was the initial velocity of the second stone?

c, what are the velocity's of the 2 stones at the instant they hit the water?

for a i used s=ut+.5a(t squared)

s = distance (50m) u = initial velocity of stone 1 (2m/s) a = gravity (9.8m/s2) and t is the time in seconds.

from that i found t = 2.99 = the right answer

for b, i tried using s=ut+.5a(t squared) again but for the second stone. So i uped the time by 1 second as it was released one second after the first so t = 3.99 s = 50m a = 9.8m/s2 and u is unknown

i got u = - 7.02 m/s

but i am told the speed is -15.4 m/s

a little help would be appreciated.

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# Homework Help: Constant Accelaration

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