Gravitation

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Question : 1
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Answer the following :
(a) You can shield a charge from electrical forces by putting it inside a hollow conductor. Can you shield a body from the gravitational influence of nearby matter by putting it inside a hollow sphere or by some other means?
(b) An astronaut inside a small spaceship orbiting around the earth cannot detect gravity. If the space station orbiting around the earth has a large size, can he hope to detect gravity?
(c) If you compare the gravitational force on the earth due to the sun to that due to the moon, you would find that the Sun’s pull is greater than the moon’s pull. (you can check this yourself using the data available in the succeeding exercises). However, the tidal effect of the moon’s pull is greater than the tidal effect of sun. Why?
Solution:  
(a) No, because the gravitational force of attraction on a point masssituated inside a spherical shell is zero.
(b) Yes, an astronaut inside the spaceship can detect the variation ingravity, if the size of the spaceship is large enough.
(c) Tidal effect depends inversely on the cube of the distance, unlikeforce, which depends inversely on the square of the distance. Since thedistance of moon from ocean water is very small as compared to thedistance of sun from the ocean water on earth. Therefore, the tidal effectof moon’s pull is greater than the tidal effect of the sun.
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