- #1

lgen0290

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## Homework Statement

A lead ball is dropped into a lake from a diving board 5.44 m above the water. It hits the water with a certain velocity and then sinks to the bottom with this same constant velocity. It reaches the bottom 4.84 s after it is dropped. (Assume the positive direction is upward.)

(a) How deep is the lake?

(c) Suppose that all the water is drained from the lake. The ball is now thrown from the diving board so that it again reaches the bottom in 4.84 s. What is the initial velocity of the ball?

## Homework Equations

h=.5(g)(t^2)

## The Attempt at a Solution

I figured that the ball would fall at -9.8m/s, but that the trip it takes would have to be divided into two parts, as when it hit the surface of the water it would stop for an instant.

I figured 5.44m=.5(-9.8 m/s)(t^2). This gave me 1.05 s(which doesn't sound realistic, but the units cancel out find). I then took the remaining time(3.79 s) and plugged it into get

h=.5(-9.8 m/s)(3.79s^2) and got 70. 38 m.

For the other problem I figured there would be no stop, so I used h=.5(-9.8)(4.84^2) and got 114.74/4.84=23.708 m/s.

What gives?