ELI5, why if you jump inside a moving train you will land on the same spot, but if you jump on the roof of a moving train, you land on a different spot?

Question

seen it on twitter and I can’t get my head around it
EDIT: thanks guys I get it now 😅

In: Physics

Answer 1

Momentum.

Inside, you are moving the same speed as the train and so is the air inside. Outside, you are moving the same speed as the train, but when you separate from the train by jumping, you are transferring momentum to the air particles you are bumping into.