It is advised not to stand near a running train. Why?

It is advised not to stand behind a vehicle with a running engine.

Why is it advisable not to talk while eating?

Why do the raindrops appear, to a passenger on a running train in a rainy day, to be falling obliquely ?

If a person stands near a fast moving train, there is a possibility of his falling-- explain.

Why we are advised not to use animal fats for cooking?

When a person is standing on earth, the treesand houses appera stationary to mim. However, when he is sitting in a running train all these obects appear to move in bakward direction. Why?