# Kinematics problem two stones falling one with velocity one at rest

1. Nov 16, 2005

### bark00

hi please can sum one help me,

a stone is dropped from he top of a cliiff at rest another stone it thrown downwards from the same point at 11ms-1. The two stones land at the same time, what is the height of the cliff,

how do u work this out i have no idea,

bark00

2. Nov 16, 2005

### Päällikkö

Which equations do you think you're supposed to use?

3. Nov 16, 2005

### bark00

thankyou for helping me,

im not sure,
ive tried using combinations of v=u+at and s=1/2 (u+v)t but i dont know where to begin.

4. Nov 16, 2005

### marlon

This is a gravity problem...Can you set up the equations for both velocity and position in the horizontal (x) and vertical (y) direction ?

ok, before actually giving specific information, i suggst you read this tutorial

The second formula you gave is not known to me. Are you sure of it ?

5. Nov 16, 2005

### Galileo

Are you sure this is the question?
So you release one stone from rest and you throw the other one vertically down at 11 m/s from the same cliff and they land omn the ground at the same time? How's that possible?

Either I misunderstood the question, you copied it wrong or the height is zero and there would be no cliff.

6. Nov 16, 2005

### bark00

hi thankyou all for the help i think i go it now i got the awnser as 128.6 metres approx

7. Nov 16, 2005

### bark00

sorry missed out second one was trown a second later.

8. Nov 17, 2005

### dx

The second formula is equivalent to $$s = V_{avg}t$$ for constant acceleration.