[sajeevml]

A stone is dropped from a tower of 100 meter height and another stone is thrown vertically up words with a velocity of 25 meter/second. When and where the two stones meet?

[ebaines]

We're not going to do your homework for you. Please show us what efforts you have made to solve this problem, and where you're getting stuck - I'm sure someone will help you once you have demonstrated some effort.

[sajeevml]

a = 9.8 ms^-2
u = 0
s = 100 m

u = 25 m/s
a = - 9.8 ms^-2
v = 0 ms^-2

hmmm, interesting. I'll need a second look at this one

s = ut + 0.5 at^2
s = 25 t - 4.9 t^2 (this is your equation for stone 2)

s = 4.9t^2 (this is the equation for stone 1)

Yes equate these equations and I get

31.8877551 = s

t = 2.551020408

[ebaines]

Not quite. Your equation for stone 1 ignores the fact that it is dropped from a height of 100m, and the sign of the acceleration due to gravity should be negative. This equation should be:

s = 100 - 4.9t^2.

Your equation for stone 2 is correct: s = 25t - 4.9t^2

Now, solve for t, and you'll get the correct answer.