# Homework Help: Need Help With As Physics Homework

1. Sep 12, 2006

### ben-newton

Hi,

I have just started AS Physics and I am doing mechanics at the moment. I am stuck on a question at the moment which I would like to know if someone can answer:

A stone is dropped from rest from a diving board which is 6 metres above the water surface of the pool below. After it hits the water it sinks to the bottom of the pool (which is 4m deep) at a constant velocity equal to the velocity with whcih it struck the water.

How long does it take the stone to fall from the board to the water?

For this question I need to use one of the following formulas:

V= u + at

x= ut + 1/2 at^2
v^2= u^2 + 2ax
x=t/2 (u+v)

Can anyone help me?

(^2) = squared

2. Sep 12, 2006

### Tomsk

Hi, you need to think about what you know, and what you need to find out. Write them all down, then pick an equation that only includes those things.

3. Sep 12, 2006

### brewnog

How fast is the stone travelling when it hits the water? (Clue, how deep is the water?)

4. Sep 12, 2006

### wxrocks

I'll bite and give you a hint -- the information about the stone after it hits the water is useless in answering the question at hand. That information "could" be used to figure out other information about the size/mass/etc about the stone, but eliminate that info for answering this question.

Now....I always like to start problems by writing down everything I know. Vi, Vf, a, position, etc. That could help you "pick" a formula.