AQA A Level Physics

Topic Questions

A LevelPhysicsAQATopic Questions7. Fields & Their Consequences7.2 Gravitational Potential

7.2 Gravitational Potential

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11 mark

Which of the following is the correct value for the value of the gravitational potential at a point infinitely far away from every massive body in the universe ?

  • infinity

  • negative infinity

  • 0

  • π

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21 mark

What are the standard units of gravitational potential ?

  • J

  • V

  • N kg–1

  • J kg–1

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31 mark

Which of the following statements regarding the gravitational potential is false ?

  • It is analogous to the electric potential at a point in an electric field

  • It is a vector quantity

  • It is defined as negative because work must be done on a mass to move the mass to infinity

  • It is inversely proportional to the distance between masses

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41 mark

A planet has a mass 5.0 × 1026 kg. 

Which of the following gives the correct value of the planet’s gravitational potential at a distance of 300 km from its centre?

  • 1.1 × 1011 J kg–1

  • –1.1 × 1014 J kg–1

  • –3.7 × 105 J kg–1

  • –1.1 × 1011 J kg–1

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51 mark

A satellite of mass 200 kg moves between two lines of equipotential above the Earth. 

It begins at point A which has a gravitational potential of –50 MJ kg–1 to a point further away, B, which has a gravitational potential of –40 MJ kg–1. This is shown in the diagram below:

7-2-mcq--q5-easy-aqa-a-level-physics

Which of the following gives the correct value of the energy required for the satellite to move from A to B?

  • 2 MJ

  • 20 MJ

  • 2000 MJ

  • 200 MJ

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11 mark

Planet Z, with centre O, is shown in the figure below.

7-2-mcq--q1-hard-aqa-a-level-physics

The radial distances OP is equal to the OX, and OQ is equal to OY, such that PX and QY are loci of Planet Z. 

Which of the following statements is incorrect?

  • The work done by the gravitational field on a test mass moving from P to Q is negative

  • The gravitational field does zero work on a test mass moving along the locus PX

  • V subscript X over V subscript Q equals fraction numerator O Y over denominator O X end fraction

  • The work done by an external force to move a test mass from Y to X is positive

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21 mark

The variation of the gravitational potential ϕ near a certain planet is shown in the table below: 

Distance from the planet’s surface / km

Potential ϕ / MJ kg–1

1700

–17.1

1900

–16.3

2100

–15.7

2300

–15.1

2500

–14.6

 

Which value gives the best approximation for the magnitude of the gravitational field strength at a point 2000 km above the planet’s surface?

  • 3 N kg–1

  • 160 N kg–1

  • –160 N kg–1

  • 3000 N kg–1

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31 mark

Which of the following statements about gravitational fields is correct? 

  • The gravitational potential is zero whenever the gravitational field strength is zero

  • The gravitational potential is negative because the gravitational field is repulsive  

  • The gradient of the gravitational potential at a point is inversely proportional to the radial distance from some massive body

  • The area under a field strength–distance curve represents the change in gravitational potential between two points

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41 mark

The relative positions of a binary star system is shown below:

7-2-mcq--q4-fig-1-hard-aqa-a-level-physics

The line XY joins the surface of the star of mass m to the surface of the star of mass M > m. 

Which graph correctly represents the variation of the gravitational potential ϕ along the line XY?  

Assume the stars have the same diameter.

7-2-mcq--q4-fig-2-hard-aqa-a-level-physics

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51 mark

The shape of equipotential surfaces in the gravitational field depends on perspective. 

The image below shows equipotential surfaces (represented by dotted lines) due to the Earth’s gravitational field in a ‘local’ frame of reference (close to the Earth’s surface) and in a ‘non–local’ frame of reference (far from the Earth’s surface):

7-2-mcq--q5-fig-1-hard-aqa-a-level-physics

Which line, A to D, in the table shows the variation of gravitational potential V with radial distance r from the Earth’s surface? 

You may assume each dotted line represents equal changes in potential ΔV and that r subscript E represents the radius of the Earth.

  • 7-2-mcq--q5-fig-2-hard-aqa-a-level-physics

  • 7-2-mcq--q5-fig-b-hard-aqa-a-level-physics

  • 7-2-mcq--q5-fig-c-hard-aqa-a-level-physics

  • 7-2-mcq--q5-fig-d-hard-aqa-a-level-physics

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11 mark

A test mass moves from the surface of the Earth to a point P in deep space, very far away from any other massive body. 

Which line, A to D, in the table shows correctly what happens to the value of the gravitational field strength and to the gravitational potential experienced by the test mass as it moves to point P? 

 

Gravitational field strength

Gravitational potential

A

B

C

D

decreases

decreases

increases

increases

decreases

increases

increases

decreases

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21 mark

When a mass moves between two points in a gravitational field, energy may be transferred. 

Which one of the following statements is correct?

  • No work is done by the gravitational force when a mass moves parallel to the direction of the field 

  • The energy transferred is independent of the start and finish points

  • Work is done by the gravitational force when a mass moves perpendicular to the field

  • The energy transferred is independent of the path followed

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31 mark

At the surface of a faraway planet, the gravitational field strength is g and the gravitational potential is V. The radius of the planet is r. 

An object weighs W on the surface of this planet and lifts off to a height 5r above the surface. 

Which line, A to D, in the table gives the weight of the object and gravitational potential at this height?

 

Weight

Gravitational potential

A

 W over 25 V over 5

B

 W over 5 V over 3

C

 W over 5 V over 5

D

 W over 25 V over 4

 

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41 mark

The figure below shows the variation of the gravitational potential ϕ between the Earth and the Moon. 

7-2-mcq--q4-medium-aqa-a-level-physics

What is the minimum energy required to launch an object of mass 5.0 kg from the Earth’s surface to the Moon’s surface?

  • 305 MJ

  • 61.0 MJ

  • 58.4 MJ

  • 300 MJ 

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51 mark

P and Q are two points near one of Jupiter’s moons, Io. The gravitational potential at P is –800 J kg–1and that at Q is –700 J kg–1. 

Which of the following statements is incorrect?

  • P is nearer to Io than Q

  • The gravitational field strength at P is greater than it is at Q

  • A body speeds up when it moves freely from P to Q

  • Work is done by an external force to move a body from P to Q

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