Question

1 (a) define gravitational field.
1
(b) a spherical planet can be considered as a point mass at its centre.
(i) on fig. 1.1, draw gravitational field lines outside the planet to represent the gravitational field due to the planet.
2
(ii) a satellite is in a circular orbit around the planet.
explain, with reference to your answer in (b)(i), why the path of the satellite is circular.
2

Explanation:

Define gravitational field

A gravitational field is a region of space where a mass experiences a gravitational force.

Describe field lines

The field lines represent the direction of the gravitational force on a test mass. Since gravity is always attractive, the field lines must point radially inward toward the center of the planet. They should be symmetrically distributed around the sphere.

Explain circular orbit

The gravitational force acts radially inward toward the center of the planet, perpendicular to the velocity of the satellite. This perpendicular force provides the necessary centripetal force, maintaining a constant speed and a circular path.

Answer:

Question 1(a)

A region of space where a mass experiences a gravitational force.

Question 1(b)(i)

The gravitational field lines are drawn as straight, radial lines pointing directly inward toward the center of the planet, distributed symmetrically around the sphere.

Question 1(b)(ii)

The gravitational force is directed radially inward toward the center of the planet, which is perpendicular to the direction of motion (velocity) of the satellite. This force acts as the centripetal force, changing only the direction of velocity and keeping the orbit circular.