Gravitational Fields

Question 1

A satellite in geostationary orbit appears to remain above the same point on the Earth
and has a period of 24 hours.
State two other features of a geostationary orbit.

Ref: 9702/41/O/N/16

Answer 1

equatorial orbit/orbits (directly) above the equator B1

from west to east

Question 2

What is meant by a field of force?

Answer 2

it is the region of space where a certain particle may experience a force/ the force acts on the particle.

Question 3

What is gravitational potential at a certain point?

Answer 3

It is the work done per unit mass in bringing a small test mass from infinity to a certain point.

Question 4

What is the formula for gravitational potential?

Answer 4

phi = GM/R

Question 5

What is meant by the line of force on a gravitational field?

Answer 5

It is the direction on a small (test) mass or the direction of acceleration on a (small test) mass.

Question 6

Why is the acceleration of free fall near the earth’s surface approximately constant?

Answer 6

1. The lines are radial
2. Near the surface, the lines are almost parallel
3. Parallel lines have a constant field strength
4. constant field strength and hence, constant acceleration of free fall.

Question 7

State Newton’s law of Gravitation.

Answer 7

The Force between 2 point mass is proportional to the product of the 2 masses and is inversely proportional to the square of their separation.

Question 8

Explain whether or not planets orbiting in a circular motion around a star are in equilibrium.

Answer 8

No, because there is a resultant force as the velocity is changing.