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        riddles >> easy >> Humming Bird--Easy Solution
        
(Message started by: vigoyal on Dec 14^th, 2004, 8:48am)

Title: Humming Bird--Easy Solution
Post by vigoyal on Dec 14^th, 2004, 8:48am

Humming Bird Problem:

No matter what are the velocities of the train, they will collide only after they both have collectively travelled 5000 miles.

So the total time traveled by the bird would be 5000/25 = 200 hours.

Now...did i do it right or is something wrong here ?

Title: Re: Humming Bird--Easy Solution
Post by towr on Dec 14^th, 2004, 1:00pm

It is the speed of the hummingbird that is irrelevant, consider what happens if the trains stand still. The hummingbird could keep flying endlessly.

Title: Re: Humming Bird--Easy Solution
Post by ImaIdiot on Dec 21^st, 2004, 1:19am

To solve the problem, wouldn't you just have to calculate the time it takes before both trains collide and multiply it by the speed of the hummingbird? Am I just stupid?

Title: Re: Humming Bird--Easy Solution
Post by THUDandBLUNDER on Dec 21^st, 2004, 1:55am

on 12/21/04 at 01:19:11, ImaIdiot wrote:

Am I just stupid?

By no means.
You are also right.

:D

Title: Re: Humming Bird--Easy Solution
Post by towr on Dec 21^st, 2004, 5:47am

Not if we want the time travelled by the bird (as opposed to path-length)..
What was the original puzzle again?

Title: Re: Humming Bird--Easy Solution
Post by THUDandBLUNDER on Dec 21^st, 2004, 6:01am

Quote:

Not if we want the time travelled by the bird...

But FLT is not required below. :P

Quote:

What was the original puzzle again?

One train leaves Los Angeles at 15mph heading for New York. Another train leaves from New York at 20mph heading for Los Angeles on the same track. The distance between LA and NY is about 5000 miles. If a bird, flying at 25mph, leaves from Los Angeles at the same time as the train and flies back and forth between the two trains until they collide, how far will the bird have traveled?

Title: Re: Humming Bird--Easy Solution
Post by Grimbal on Dec 21^st, 2004, 7:55am

Considering that the hummingbird is now squashed between the trains and there are hundreds of woulded people in and around the train, some in a serious condition, who cares how far the bird travelled? >:(

Uh... anyway, the time travelled is still easier, it is the TTC (or time to collision): 5000/(15+20) = 142.857 hours. Almost 6 days! The bird must have been nearly dead anyway.

Title: Re: Humming Bird--Easy Solution
Post by SteelSoul on Jun 11^th, 2005, 12:35pm

The question is NOT the time travelled but how far meaning how many miles she flew.
of course once you calculate the time as you all did so well, you just have to multiply it by the speed of the bird which DOES makes the speed relevant. :P

Title: Re: Humming Bird--Easy Solution
Post by Monty on Jul 14^th, 2005, 12:44am

This problem is one of the most debatable in the physics world.

Theoritically, as the trains approach closer, the speed of bird being greater than any of the train, the time taken by the bird to reach the opposite train would go on decreasing.
t=d/s, s being the relative speed
s remaining fixed (either 20+25 or 15+25)
d goes on decreasing. Hence t goes decreasing.

Consider a case when the distance is .0001 mile.
The time taken by bird is t=.0001/40=0.0000025 hrs or 0.009s.
The closer the trains, the faster the bird. This leads to the path of bird ending up at an infinity value.

But practically, we know that the trains would collide in t=5000/35=143 hrs. So the bird path has to be a finite number however high it might be.

Title: Re: Humming Bird--Easy Solution
Post by towr on Jul 14^th, 2005, 1:37am

but the speed of the bird is constant, aside from direction.
(And even otherwise limited by the speed of light. So fo a finite amount of time you always have a finite path)

Title: Re: Humming Bird--Easy Solution
Post by raprap on Jul 15^th, 2005, 3:28am

Imagine a world where the speed of light was 30 mph. Relativity still applies.

How long would the Hummingbird Hum?

Rap

Title: Re: Humming Bird--Easy Solution
Post by towr on Jul 15^th, 2005, 3:33am

Depends on who the observer is, if you want to involve relativity.

Title: Re: Humming Bird--Easy Solution
Post by raprap on Jul 15^th, 2005, 4:03am

;DA hobo making a bean souree on a campfire near the track 2142 6/7 miles east of LA.

Rap