# Homework Help: A Tiny Help please!

1. Nov 16, 2005

### xytos

A 50.0 kg diver steps off a diving board and drops straight down into the water. The water provides an adverage net force resistance of 1500N to the driver's fall. If the driver comes to rest 5.0M below the water's surface, what is the total distance between the board and the driver's stopping point underwater?
The Given:
mass: 50.0kg
resistant force: 1500N​
Can someone tell me how to get velocity?? I've tried everything i could think of...
D=1/2mv^2/F;

Anything else i can do??

2. Nov 16, 2005

### Tom Mattson

Staff Emeritus

You were given more than that. You were told that the diver's final velocity is zero, you were told that his initial velocity was also zero (that is implied by the word "drops"), and you were told that his final displacement is 5 m below the surface of the water.

I'm not going to just tell you how to do the problem (we don't do that here at Physics Forums) but what I will do is give you some helpful advice.

First of all: Don't just throw equations at the problem. Think about the problem.

OK, you've actually got two parts to this problem: The part where the diver is in the air, and the part where he's in the water. While he's in the air you can assume that the only force acting on him is gravity. While he's in the water you have two forces acting: gravity and the drag force from the water.

Now, you don't know how far it is from the board to the surface of the water, so you're going to have to represent that distance with a variable.

Try to answer these questions, in order. If you can do that then you can solve half of the problem.

1.) Set a convenient point to serve as the "zero" of displacement.
2.) Analyze the motion in the water first. What were you given?
3.) What were you asked for?
4.) What equation contains all of those quantities? Use that equation in the next step.
5.) What is the numerical value of the unknown?

Give that a shot. If you can complete step 5 then you will have solved half the problem, and then we can get to work on the other half.