Q:

if someone would for example shoot a bullet, standing on the ground into a train. As soon as the bullet enters the train, the train matches up the speed of the bullet. They are now travelling, same speed. How would it look like for someone inside the train? would the bullet hover in the air or double up its speed?

- jimmi (age 19)

Sweden

- jimmi (age 19)

Sweden

A:

Hello Jimmi,

To an observer outside of the train the bullet will follow its regular path, an arc with the horizontal velocity of the train and the vertical velocity increasing as v = -gt where g is the acceleration of gravity. It will eventually bump into the floor of the train. To an observer inside the train the bullet will suddenly appear. Its velocity along the direction of the train is zero. Its vertical velocity will be the same as that seen by the outside observer, v = -gt, and it will fall to the floor. This is an example of Galilean relativity.

LeeH

*(published on 05/03/2014)*