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Q1. Can gravitational potential energy be 0. If yes how?

Solution

Yes, gravitational potential energy can be 0 when there is an infinite separation between the two interacting bodies.

Q2. G is called Universal Gravitation Constant. Why?

Solution

G is called Universal Gravitation Constant because its value i.e. 6.67 x 10^-11 Nm²kg^-2 is constant thought the universe.

Q3. Does a pendulum vibrate in an artificial satellite?

Solution

No a pendulum doesn't vibrate in an artificial satellite as there is no gravity. The value of g = 0.

Q4. Name a polar satellite. State its uses.

Solution

Sea star is a polar satellite. Polar satellites are used for 1.      Getting cloud images, 2.      Atmospheric data, 3.      To detect the ozone hole.

Q5. In a gravitational field there is a point A where the gravitational potential is 0. Will the gravitational energy be 0?

Solution

In a gravitational field there is a point A where the gravitational potential is 0. The gravitational energy is not necessarily 0 it can have other value also.

Q6. Do the body experiencing weightlessness possess inertia?

Solution

Yes, the body experiencing weightlessness possesses inertia due to their mass.

Q7. State the conditions in which a body can be weightless.

Solution

A body can be in a weightless state when a)     The body is taken at the center of the earth. b)     When body is taken at null points i.e. points where gravitational forces due to different masses cancel out. c)      When body is lying in a freely falling lift. d)     When body is inside a spacecraft or satellite orbiting around the earth.

Q8. On which two quantities does the gravitational force depend?

Solution

Gravitational force depends on i)                    Mass of the two bodies ii)                   Distance between the two bodies

Q9. Which law explains the rotation of planets around the sun and the rotation of satellites around the planets?

Solution

The universal law of gravitation forms the basis of the explanation for the rotation of planets around the sun and the rotation of satellites around the planets.

Q10. We use multi-stage rocket for launching a satellite. Why?

Solution

We use a multi-stage rocket for launching a satellite to reach the desired height and gain velocity for the rocket. When the rocket is fired, the fuel of the first stage starts burning. This helps the rocket reach a desired height with a definite velocity. Then, the first stage detaches and the second stage starts burning. This helps in attaining a desired direction and increase in height and velocity. When the fuel for this stage is burnt completely the last stage gives the desired height and velocity to the rocket.