# Linear motion

1. Jan 22, 2008

### Cantworkit

[SOLVED] linear motion

1. The problem statement, all variables and given/known data
A bird is flying 30 m above a lake when it drops a fish. Another bird at 35 m immediatley dives and catches the fish before it hits the water. What is the initial velocity of the second bird?

2. Relevant equations
h=h0 + v0t - gt^2/2

3. The attempt at a solution

At some point the height of the fish and the height of the second bird are equal.
hfish = 30 - gt^2/2.
hbird = 35 + v0t - gt^2/2. I can solve for t, but I don't know how to get v0.
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 22, 2008

### blochwave

The way the problem is worded I'm assuming the bird catches the fish immediately before it hits the water? (Otherwise it's impossible without more info, at best you can find the minimum necessary initial speed of the bird by doing as follows...)

If so, you can find t by finding how long it takes the fish to hit the water, and assuming the bird grabs it at that instant.

This is also equivalent to setting Hfish and Hbird equal to 0 and solving the equations simultaneously for t and Vo