# If you were in a smooth-riding train with no windows, could you sense the difference between...

## Question:

If you were in a smooth-riding train with no windows, could you sense the difference between uniform motion and rest or between accelerated motion and rest?

1. Both accelerated and uniform motion can be sensed.

2. Only uniform motion can be sensed.

3. Only accelerated motion can be sensed.

4. No motion can be sensed.

## Velocity Is Relative:

Velocity is relative and the magnitude depends upon the different frames of reference.

For e.g. A person sitting next to you in a moving car will say that you are at rest but for a girl standing outside, you are in motion. So, one says that you are moving with a velocity (say 40 km/h) and another person says that your velocity is zero. Therefore, it is relative and not absolute for everyone.

If you are sitting inside a train that has a fixed velocity and all the windows are black or opaque or there is no way to look outside. Then, you cant perceive whether the train is moving or not. As, when the speed is fixed then the acceleration is zero and you will feel no force acting on you or acting on any other object placed over theirs. With that, there's no experiment in physics that can tell you whether the train is moving or not or all the laws of physics remains the same in all inertial frames of references (zero acceleration). For e.g. you throw a ball vertically upwards in a train, it will follow all the physics rules equally, either the train is moving or staying.

On the other hand, when the train accelerates, it will exert a force on everything placed inside it in the opposite direction (called pseudo-force). And it can be observed by detecting sloshing of water in a bowl.

Option 3 is correct as only accelerated motion can be sensed.