IBPhysicsSLTopic QuestionsFieldsGravitational Fields

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First teaching 2023

First exams 2025

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Gravitational Fields (SL IB Physics)

Topic Questions

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1
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What is the correct relationship between the gravitational force and the distance between two point masses?

  • F proportional to 1 over G

  • F proportional to 1 over m

  • F proportional to 1 over r squared

  • F proportional to r squared

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2
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The force, F between two point masses is 10 N. The distance, r between the two masses is doubled. 

What is the new force between the two masses?

  • 2.5 N

  • 5 N

  • 20 N

  • 100 N

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3
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Which expression best describes the relationship between the orbital time period, T and the orbital radius, r?

  • T cubed proportional to r squared

  • T squared equals r cubed

  • T squared proportional to 1 over r cubed

  • T squared proportional to r cubed

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4
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Which of the following is not an equation which can be used to calculate g, the gravitational field strength?

  • g equals F over m

  • g equals fraction numerator G M over denominator r squared end fraction

  • g equals F m

  • g equals fraction numerator w e i g h t over denominator m a s s end fraction

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5
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Which of the following statements about gravitational force is true?

  • Gravitational force has a finite range

  • A greater gravitational force is exerted on objects with larger mass

  • On planets with a large value of g, the gravitational force per unit mass is smaller than on planets with a smaller value of g

  • An object's mass changes depending on the gravitational field strength at that point

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6
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An alien of mass 100 kg lives on a planet with a gravitational field strength of 50 N kg−1. 

What is the weight of the alien on this planet?

  • 5000 N

  • 1000 N

  • 0.05 N

  • 100 N

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7
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A commercial low-orbit space flight carries a passenger of mass 70 kg.

What is the approximate gravitational force of attraction between the Earth and the passenger?

  • 0 N

  • 7 N

  • 700 N

  • 7000 N

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8
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A planet has twice the radius of the Earth and 4 times the mass. Assume the planet is spherical and of uniform density.

If the magnitude of the gravitational field strength on Earth is g, what is the magnitude of the gravitational field strength on the surface of the planet?

  • 4g

  • 8g

  • 2g

  • g

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9
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Which graph, plotted on logarithmic axes, shows Kepler's Third Law for the planets in our Solar System?

  • 6-2-newtons-law-of-gravitation-sl-mcqs-easy-q10-answer-a

  • 6-2-newtons-law-of-gravitation-sl-mcqs-easy-q10-answer-b

  • 6-2-newtons-law-of-gravitation-sl-mcqs-easy-q10-answer-c

  • 6-2-newtons-law-of-gravitation-sl-mcqs-easy-q10-answer-d

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10
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The gravitational field strength at a point P in a gravitational field is defined as:

The force...

  • per unit mass on a mass placed at P

  • on a mass placed at P

  • per unit mass on a small point mass placed at P

  • on a small point mass placed at P

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1
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The surfaces of two spherical asteroids are separated by distance d.  Asteroid A1 has a volume of 113 km3, asteroid A2 has a surface area of 18.1 km2. 

The density of A1 is 600 kg m−3 and the density of A2 is 1300 kg m−3. 

If the gravitational force between the asteroids is 73 MN, what is the distance from the surface of A1 to the surface of A2?

  • 3 km

  • 20 km

  • 24 km

  • 20 000 km

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2
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The gravitational field strength on the surface of a planet orbiting a star is 6.5 N kg–1. The star has twice the density of the planet and the diameter of the star is 1000 times greater than the planet. 

How many times greater is the weight of an object on the surface of the star compared to the weight of the object on the surface of the planet ?

  • 2000

  • 1000

  • 500

  • 100

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3
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At a point above a planet’s surface and a distance x from its centre, the gravitational field strength is 4 N kg–1. At the planet’s surface, the field strength is 8 N kg­­–1­. 

Which one of the following gives the value for the radius of the planet ?

  • x over 5

  • fraction numerator x over denominator 2 square root of 2 end fraction

  • fraction numerator x over denominator square root of 2 end fraction

  • x over 2

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4
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An astronaut on the surface of a moon of mass 7 × 1021 kg stands atop a large hill 100 m above ground level. The gravitational field of the moon is too weak to retain an atmosphere. 

They throw a projectile with an initial horizontal velocity of 2 m s–1 which subsequently lands 12 m away from the base of the hill. 

Which of the following gives the correct value for the radius of the moon?

  • 8.3 × 1010 m 

  • 2.9 × 105 m

  • 1.2 × 105 m

  • 1.4 × 1010 m

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1
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The mass of a potential landing module heading for Jupiter is 4000 kg. The gravitational field strength on Jupiter is roughly 2.5 times that on Earth. What is the weight of the landing module on Earth?

  • 4000 N

  • 100 000 N

  • 10 000 N

  • 40 000 N  

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2
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A planet has triple the mass of Earth and a third of its radius. What is the gravitational field strength on the surface of the planet?

  • 10 N kg-1

  • 270 N kg-1

  • 90 N kg-1

  • 240 N kg-1

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3
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The diagram below shows three uniform masses in a straight line.

q13_newtons-law-of-gravitation_ib-sl-physics-mcq

The resultant gravitational force on the 1 kg mass is zero if the distance x is:

  • 45 over 7 straight m

  • 45 m

  • 27 over 5 straight m

  • 35 m

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4
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The gravitational force between two identical uniform spheres of mass M is F when the distance between them d.

q14_newtons-law-of-gravitation_ib-sl-physics-mcq

If the radius of each sphere is x, what is the correct expression for mass, M?

  • fraction numerator straight F left parenthesis d plus 2 x right parenthesis squared over denominator straight G end fraction

  • square root of fraction numerator straight F d squared over denominator straight G end fraction end root

  • square root of fraction numerator straight F left parenthesis d plus 2 x right parenthesis over denominator straight G end fraction end root

  • square root of fraction numerator straight F left parenthesis d plus 2 x right parenthesis squared over denominator straight G end fraction end root

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5
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A spherical planet of uniform density has two times the mass of the Earth and three times the average radius. The magnitude of the gravitational field strength at the surface of the Earth is g. What is the gravitational field strength at the surface of the planet?

  • 3 over 4 g

  • 2 over 3 g

  • 2 over 9 g

  • 18g

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6
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The inverse square law means that halving the radius of a planet results in quadrupling the gravitational field strength at its surface.

The centres of two planets are separated by a distance R. The gravitational force between the two planets is F. What will the force between the planets be when their separation increases to 4R?

  • F over 16

  • 4F

  • F over 4

  • F

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7
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A mass at point P gives rise to a gravitational field strength g at point X as shown.

q18_1_newtons-law-of-gravitation_ib-sl-physics-mcq

An identical mass is placed at point Q as shown.

q18_2_newtons-law-of-gravitation_ib-sl-physics-mcq

What is the resultant gravitational field strength at X in this new situation?

  • zero

  • between g and zero

  • between 2g and g 

  • greater than 2g

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8
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A spacecraft travels away from Earth in a straight line with its motors shut down. At one instant, the speed of the spacecraft is 5.7 km s-1. After a time of 1000 s, the speed is 5.2 km s-1. The gravitational field strength acting on the spacecraft during this time interval is:

  • –5 × 10–4 N kg–1

  • 5 × 101 N kg–1

  • –5 × 10–1 N kg–1

  • –1 × 101 N kg–1

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9
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Which of the following statements about uniform gravitational fields is incorrect?

  • The field strength is equal at every point in a uniform gravitational field

  • The acceleration of freefalling bodies is dependent on their mass

  • The field lines in a uniform gravitational field are parallel to each other  

  • There is a uniform gravitational field near the Earth’s surface

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