Solving Linear Motion: Bird Catching Fish

Click For Summary
A bird drops a fish from 30 m above a lake, while another bird at 35 m dives to catch it. The problem involves determining the initial velocity of the second bird using the equation for linear motion. The key is to find the time it takes for the fish to reach the water and assume the second bird catches it just before impact. By setting the heights of both the fish and the bird equal, simultaneous equations can be solved for time and initial velocity. The discussion concludes that without additional information, only the minimum necessary initial speed can be calculated.
Cantworkit
Messages
12
Reaction score
0
[SOLVED] linear motion

Homework Statement


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. Homework 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.
 
Physics news on Phys.org
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
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

Similar threads

Replies
7
Views
1K
  • · Replies 31 ·
2
Replies
31
Views
4K
Replies
11
Views
3K
Replies
13
Views
2K
Replies
14
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 9 ·
Replies
9
Views
8K
  • · Replies 11 ·
Replies
11
Views
4K
  • · Replies 1 ·
Replies
1
Views
7K
  • · Replies 11 ·
Replies
11
Views
2K