Hi all.
The following problem was posted by someone on another forum:
Who is right, the poster or their friend? I myself agree with the poster's friend that the bird will be stationary relative to the train passengers – or at any rate the bird won't be moving forwards or backwards relative to the train, but may be moving sideways relative to the train since it has to move sideways to approach the train. The poster nevertheless disagrees, claiming that it is counterintuitive to see a bird flapping its wings like mad and yet going nowhere.I have been having an ongoing disagreement with a friend about the outcome of a hypothetical situation involving a train and a bird. I'm hoping someone from this forum will be able to help me understand the physical laws that support my argument OR shoot me down in flames and tell me where I’ve gone wrong.
Let's imagine that there is a train travelling North at a constant speed of 50mph. Outside, there is a bird flying parallel with the train that is also moving North at a constant speed of 50mph. (with me so far?). The bird then edges closer to the train and while still facing North the bird enters the train via a window.
I propose that once inside the train, assuming the bird continues to flap at its constant rate; it will fly towards the front of the train. Someone inside the train will observe the bird moving forward through the train at 50mph.
My friend proposes that the bird will stay at the same point in the train that it entered. I.e. if it entered at the back of coach E, even though it’s still flapping like mad, it will remain at the back of coach E and will appear stationary to an observer within the train.
What worries me is how blindingly obvious it seems to me that I’m right. This feeling often coincides with me being wrong.
So, am I (and the poster's friend) wrong? And if so, where did we go wrong?![]()