# Homework Help: Projectile Motion

1. Sep 7, 2008

### Pakbabydoll

A mountain climber stands at the top of a 59.4 m cliff that over hangs a pool of water. He throws 2 stones vertically downwards 1.77s apart and they cause a single splash.
first stone initial velocity= -2.06m/s
acceleration of gravity 9.8m/s^2
How long after release of first stone will the two hit water? in units of s.

2. whats the formula to do this problem. I am completely lost!

2. Sep 7, 2008

### LowlyPion

Which of the kinematic formulas below do you think would be useful getting you the answer?
https://www.physicsforums.com/showpost.php?p=905663&postcount=2

3. Sep 7, 2008

### Pakbabydoll

initially I started using
x = x_0 + v_0 t + (1/2) a t^2
and
v = v_0 + a t
but I always end up with two unknowns (A and T)
so now I am completely lost.

4. Sep 7, 2008

### LowlyPion

Start solving for what you can then?

You know the height of the cliff.
You know initial velocity.

Just curious why you think "a" is unknown when they give it to you as 9.8 m/s2.

5. Sep 8, 2008

### Pakbabydoll

I got it thanks :) I was just having a panic moment with that problem.

6. Sep 8, 2008

### LowlyPion

Just remember to take a breath then next time and start working from what you know and develop what you can. Then who knows but you may arrive at the answer?

Good luck.