# Diver physics

1. Oct 29, 2006

### tennisacerg

A 65 kg person dives into the water from the 10 m platform.

a)What is her speed as she enters the water?

b)She comes to a stop 2.0 m below the surface of the water. What net force did the water exert on the swimmer?

2. Oct 29, 2006

### Ja4Coltrane

Part A is simple kinematics.
recall Vf(sq)=Vi(sq)+2(a)(d)
(carefull--a=g which is negative.)

Part B is not realistic, but can be solved easily with an energy approach. Remember that gravity does a total work of (mg)(distance). Don't forget about the distance into the water--that matters. If the diver stops, the work by gravity is the same as the work by the water= (Fwater)(distance)

3. Oct 29, 2006

### geoffjb

As was already stated:

$$v_{f}^{2}=v_{i}^{2}+2ad$$

You can solve for final velocity from this.

Using the same equation, you can determine part b. You will, of course, be required to manipulate the equation to solve for a, and then multiply this result by the diver's mass to determine the force applied by the water.

Watch your signs throughout! (I.e. make positive either up or down, and then stick with that throughout.)