# 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 - Physics

MCQ

A free 238U 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

#### Options

• x + v t

• x − v t

•  x

• depends on the direction of the train

#### Solution

x
The moving train does not put any extra force on the alpha particle and the recoiling nucleus. So, the distance between the alpha particle and the recoiling nucleus at a time t after the decay, as measured by the passenger, will be same as before, i.e. x.

Concept: Newton’s Second Law of Motion
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#### APPEARS IN

HC Verma Class 11, Class 12 Concepts of Physics Vol. 1
Chapter 5 Newton's Laws of Motion
MCQ | Q 14 | Page 78