# Homework Help: Kinematics ball is dropped

1. May 5, 2014

### Dr.azwar

A ball is dropped from a 100m cliff. at the same time another ball is thrown up such that it has enough velocity to reach the top. at what distance from top of the cliff will the two balls meet?

2. May 5, 2014

### Staff: Mentor

Please use the homework template, and tell us what you have done so far.

Chet

3. May 5, 2014

### Dr.azwar

let the two balls pass at t sec
the initial velocity of the ball is =
v^2-u^2=2as
0-u^2=2*-10*100
u=20(5)^1/2
therefore displacement of ball in tsec=
s1=ut+1/2a(t)^2
s1=(20(5)^1/2)t- 1/2g(t)^2..........................1
the displacemt of other ball in t sec =
s2=1/2g(t)^2...................................2
eq 1 +eq 2=100
(20(5)^1/2)t=100
t=(5)^1/2
therefore they will pass each other at
1/2g(5)=25m from the top

4. May 5, 2014

### Staff: Mentor

So you didn't need any help with it after all?

Chet

5. May 5, 2014

### Dr.azwar

i just wanted to know wheather my answer is correct