U6 2023 Gravitational Fields Revision for Mock

The Earth can be assumed to be a uniform sphere of radius R.

What is the mean density of the Earth?

Which one of the following statements about gravitational fields is incorrect?

• Moving a mass in the direction of the field lines reduces its potential energy.

• A stronger field is represented by a greater density of field lines.

• Moving a mass perpendicularly across the field lines does not alter its potential energy.

• At a distance r from a mass the field strength is inversely proportional to r.

A spherical planet of uniform density ρ has radius R.

Which line, A to D, in the table gives correct expressions for the mass of the planet and the gravitational field strength at its surface?

• A

• B

• C

• D

Which one of the following graphs correctly shows the relationship between the gravitational force, F, between two masses and the distance, r, between them?

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Electric and gravitational fields can be represented in similar ways.

Which of the diagrams below cannot be used for a gravitational field?

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A spacecraft of mass m is at the mid-point between the centres of a planet of mass M₁ and its moon of mass M₂. If the distance between the spacecraft and the centre of the planet is d, what is the magnitude of the resultant gravitational force on the spacecraft?

Mars has twice the mass of Mercury and is 4 times further away from the Sun.

The ratio of the gravitational force from the Sun on Mercury to the gravitational force from the Sun on Mars is

• 0.5

• 2.0

• 8.0

• 32

Masses of M and 2M exert a gravitational force F on each other when the distance between their centres is r. What is the gravitational force between masses of 2M and 4M when the distance between their centres is 4r?

• 0.25 F

• 0.50 F

• 0.75 F

• 1.00 F

A planet has a radius half the Earth’s radius and a mass a quarter of the Earth’s mass. What is the approximate gravitational field strength on the surface of the planet?

• 1.6 N kg^–1

• 5.0 N kg^–1

• 10 N kg^–1

• 20 N kg^–1

A spherical planet of uniform density ρ has radius R.

Which line, A to D, in the table gives correct expressions for the mass of the planet and the gravitational field strength at its surface?

• A

• B

• C

• D