Question

A free ${}^{238}$U nucleus kept in a train emits an alpha particle. When the train is stationary, a nucleus decays and a passenger measures that the separation between the alpha particle and the recoiling nucleus becomes x at time t after the decay. If the decay takes place while the train is moving at a uniform velocity v, the distance between the alpha particle and the recoiling nucleus at a time t after the decay as measured by the passenger is:

• A. $x+vt$
• B. $x-vt$
• C. $x$
• D. depends on the direction of the train

Answer 1

Answer: (C)

$x$

As the both the nucleus and the passengers are in train so they will move with uniform velocity and there is no relative motion in between them. Thus, the distance between the alpha particle and the recoiling nucleus will be same as before he has measured i.e $x$