Mark the correct statement:
$(i)$ Escape velocity does not depend on the mass of the body.
$(ii)$ If the total energy of a satellite becomes positive,it escapes from the Earth.
$(iii)$ The orbit of a geostationary satellite is called a parking orbit.

Identify the correct option.

$A$ spacecraft travels in a straight line from the Earth to the Moon. How will its weight change during this journey?

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 space ship 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. However,the tidal effect of the moon's pull is greater than the tidal effect of the sun. Why?

When a satellite in a circular orbit around the earth enters the atmospheric region,it encounters small air resistance to its motion. Then

$A$ tunnel is dug in the Earth across one of its diameters. Two masses $m$ and $2m$ are dropped from the ends of the tunnel. The masses collide, stick to each other, and perform $S.H.M.$ The amplitude of the $S.H.M.$ will be: