OCR A Level Physics

Topic Questions

5.7 Gravitational Fields

11 mark

The Earth is surrounded by a gravitational field.

Which of the following statements is/are correct about the gravitational field lines near the surface of the Earth.

1      They are parallel.
2      They show the direction of the force on a small mass.
3      They are equally spaced.

  • Only 1

  • Only 1 and 2

  • Only 2 and 3

  • 1, 2 and 3

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1
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1 mark

The gravitational force between two point-mass objects X and Y is F1.

The mass of X increases and the distance between X and Y is halved.

Which statement about the new gravitational force F2 between these two objects is correct?

  • 0 < F2 < 0.25F1

  • F2 > 4F1

  • F2 = F1

  • 2F1 < F2 < 4F1

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2
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1 mark

A space probe travels from the Earth to the Moon, where the distance between the centre of the Earth and the Moon is r. When the probe is halfway to the Moon, it has a driving force of F, and is travelling at a constant velocity.

What is the forward force FA equivalent to?

  • fraction numerator 2 G m subscript P r o b e end subscript over denominator r squared end fraction left parenthesis M subscript E a r t h end subscript minus M subscript M o o n end subscript right parenthesis

  • fraction numerator 4 G m subscript P r o b e end subscript over denominator r squared end fraction left parenthesis M subscript E a r t h end subscript minus M subscript M o o n end subscript right parenthesis

  • fraction numerator 2 G M subscript M o o n end subscript M subscript E a r t h end subscript m subscript P r o b e end subscript over denominator r squared end fraction

  • fraction numerator 4 G M subscript E a r t h end subscript over denominator r squared end fraction left parenthesis M subscript M o o n end subscript minus space m subscript P r o b e end subscript right parenthesis

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3
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1 mark

Satellite X orbits the Earth at distance h above its surface and experiences gravitational field strength gX. Satellite Y has half the mass of Satellite X but orbits the Earth at double the distance and experiences gravitational field strength gY.

Given that the radius of the Earth is r, what is the ratio of g subscript X over g subscript Y equivalent to?

  • fraction numerator r plus 2 h over denominator r plus h end fraction

  • open parentheses r plus h close parentheses squared over open parentheses r plus 2 h close parentheses squared

  • fraction numerator open parentheses r plus 2 h close parentheses squared over denominator open parentheses r plus h close parentheses 2 end fraction

  • 4

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4
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1 mark

Below is a diagram of two asteroids, P and Q, that are equidistant from Asteroid R. The mass of Asteroid R is m, and the masses of P and Q are both 3m. The gravitational force of P on Q is perpendicular to the gravitational force of R on Q.

5-7-mcq-h-q4-ocr-al-physics

By modelling the asteroids as spheres, what is the resultant force on Asteroid R?

  • fraction numerator 3 square root of 2 G m squared over denominator r squared end fraction

  • fraction numerator 6 G m squared over denominator r squared end fraction

  • fraction numerator 4 square root of 2 G m over denominator r squared end fraction

  • fraction numerator 3 G m squared over denominator r squared end fraction

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11 mark

A graph of y against distance r from the centre of a planet is shown below.

q9-paper-1-june-2017-ocr-a-level-physics

The graph shows that y is inversely proportional to r2.

Which quantity is best represented on the y-axis of the graph?

  • Period of a satellite orbiting the planet.

  • Gravitational potential of the planet.

  • Gravitational field strength of the planet.

  • Kinetic energy of a satellite orbiting the planet.

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