Is this bee & train really stopped

Question

bumble bee reverses direction when hit by train travelling in opposite direction, so bee's speed goes from x to -t, through 0 at which point it's stopped, therefore train must also be stopped ?? so was it actually moving in the 1st place ??

Answer 1

A train weighing 4 tonnes, travelling at 100 mph collides with a bumblebee weighing 0.21g, travelling at 4 meters per second.

Estimated momentum of train =

4,000,000 kg x 45 meters per second =

180,000,000 kg ms-1

Estimated momentum of bumblebee =

0.00021 kg x 4 meters per second =

0.00084 kg ms -1

In this example the squashed bumblebee reduces the train's momentum from 180,000,000kg ms-1 to

179,999,999.99916kg ms-1

This would slow the train down to 44.9999999979 ms-1, according to the law of conservation of momentum.

I doubt if the train driver would notice, but the bee certainly would!

Answer 2

The train is never stopped. Rather, the train's windscreen has a degree of flexibility, and when encountering the bumblebee, it will bend slightly at the point of impact, absorbing the energy of the impact, then it will straighten back up again. But most of the "stopping" is done to the bumblebee, since it's very soft.