You are launched upward inside a very large railway coach in a horizontal positi
ID: 3161199 • Letter: Y
Question
You are launched upward inside a very large railway coach in a horizontal position with respect to the surface of Earth, as shown in the figure below. After the launch, but while the coach is still rising, you release two ball bearings at opposite ends of the train and at rest with respect to the train. Riding inside the coach, will you observe the distance between the ball bearings to increase, decrease, or remain the same with time? Now you ride in a second railway coach launched upward in a oriented in a vertical position with respect to the surface of Earth. Again you release two ball bearings at opposite ends of the coach and at rest with respect to the coach. Will you observe these ball bearings move together, apart, or not move relative to one another? In either of the cases described above, can you, the rider in the railway coach, distinguish whether the coach is rising or falling with respect to the surface of Earth solely by observing the ball bearings from inside the coach? What do you observe at the moment the coach stops rising with respect to Earth and begins to fall?Explanation / Answer
To answer this question, there are some assumptions that I have to make
1. The railway coach is moving with a constant velocity once it has departed the earth.
2. The railway coach is very very long........like the one in the diagram!
a) Distance b/w ball bearings will decrease as coach rises. The direction of g (acceleration due to gravity) is always directed towards the centre of the earth. As the coach rises, the g develops a component in the horizontal direction. The left ball develops this component towards the right while the right develops it towards the left and this makes them come together.
b) g decreases when one moves away from the surface of the earth. So, the body that is far away has a lower g than the body closer to the earth. Hence, the separation will increase.
c) It is not possible for the observer inside the coach to understand if the coach is rising or falling with respect to the earth. This is because in both cases, g is always pointing towards the centre of the earth and has a lower value with increasing distance. I have assumed uniform velocity.
However, when the direction of motion changes, an acceleration is involved. This can be realized by the observer as he will see a temporary phenomenon of reversal of the direction of motion in both cases because of the fictious force (or pseudo forces) acting on them due to the acceleration. The effect will be more pronounced in the second case, wherein the balls will move towards each other for a brief period before moving away from each other,
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