D.1 Gravitational fields questions for IB Physics

101 questions on Gravitational fields, written by Augment in the style of IB exam papers. Six of them are below in full, to answer on paper.

IB Physics
Part of D Fields
SL and HL

Questions by paper and level

SL and HL questions are for students at either level. HL only questions cover what only HL students study.

Paper	SL and HL	HL only	All
Paper 1A	25	12	37
Paper 1B	4	1	5
Paper 2	33	26	59
Every paper	62	39	101

Counted on 10 November 2026

Questions to try

Written by Augment in the style of IB exams, not past papers. Answer them on paper, then check each one against its markscheme with a free account.

Question 1 · PHY-00778Paper 1A · 1 mark

In a torsion-balance experiment, two small lead spheres attract each other with a gravitational force $F$ . One sphere is replaced by a sphere of twice the mass and the separation of the centres of the spheres is tripled. What is the new gravitational force between the spheres?

A
$\frac{2 F}{9}$
B
$\frac{2 F}{3}$
C
$\frac{9 F}{2}$
D
$6 F$

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Question 2 · PHY-01337Paper 1B · 12 marks

A group of students measure the acceleration of free fall $g$ in the laboratory. A steel ball is held by an electromagnet above a light gate. When the electromagnet is switched off, the ball falls from rest and a timer measures the time $t$ the ball takes to reach the light beam. The distance $s$ is measured from the bottom of the ball to the light beam with a metre rule. The diagram is not to scale.

An electromagnet holds a steel ball above a light gate. A vertical double arrow labelled s runs from the bottom of the ball down to the dashed light beam of the gate. Wires connect both the electromagnet and the light gate to a timer.

For each value of $s$ the students record $t$ five times. The readings for $s = 0.650$ m are:

Trial	1	2	3	4	5
$t$ / s	0.364	0.371	0.366	0.369	0.365

(a)(i)
Determine the mean value of $t$ for $s = 0.650$ m and its absolute uncertainty.
2 marks
(a)(ii)
Calculate the percentage uncertainty in $t^{2}$ for $s = 0.650$ m.
2 marks
(b)
The students' theory is that $s = \frac{1}{2} g t^{2}$ . They plot the variation of $s$ with $t^{2}$ . The horizontal error bars show the uncertainty in $t^{2}$ ; the uncertainty in $s$ is too small to show. The line of best fit is drawn.
Outline why plotting $s$ against $t^{2}$ is a suitable way to test the theory.
2 marks
(c)
Determine, using the graph, a value for $g$ .
3 marks
(d)
The line of best fit does not pass through the origin. Suggest one reason for this.
1 mark
(e)
The radius of the Earth is $6.37 \times 10^{6}$ m. Calculate, using your answer to (c), the mass of the Earth.
2 marks

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Question 3 · PHY-00222Paper 2 · 10 marks

A lunar lander of mass 15 000 kg is descending vertically towards the surface of the Moon. At a height of 150 m it is moving downwards at $12 {m s}^{- 1}$ . Its engine then provides a constant upward force, so that the lander decelerates uniformly and comes to rest at a height of 4.0 m. The engine is then switched off and the lander falls to the surface.

The following data are given:

mass of the Moon $= 7.35 \times 10^{22} kg$
radius of the Moon $= 1.74 \times 10^{6} m$

Ignore the change in mass of the lander due to the fuel used.

(a)
Show that the gravitational field strength at the surface of the Moon is about $1.6 {N kg}^{- 1}$ .
2 marks
(b)
Calculate the magnitude of the deceleration of the lander while the engine is on.
2 marks
(c)
Calculate the time for which the engine is on.
1 mark
(d)
Determine the force provided by the engine during the deceleration.
2 marks
(e)
Calculate the speed with which the lander reaches the surface.
2 marks
(f)
Outline why the lander cannot use a parachute to slow its descent.
1 mark

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Question 4 · PHY-00779Paper 1A · 1 mark

Newton's law of gravitation, $F = G \frac{m_{1} m_{2}}{r^{2}}$ , is used with $r$ equal to the distance between the centres of the two bodies. For which pair of bodies does this give the exact gravitational force between them?

A
two long, thin rods lying parallel and close to each other
B
a spacecraft just above the surface of an irregularly shaped asteroid
C
a climber and the mountain beside which she is standing
D
two uniform spheres whose surfaces are touching

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Question 5 · PHY-01338Paper 1B · 10 marks

A group of students photograph Jupiter through a small telescope on many clear nights over two months. On each image they measure the position of each of Jupiter's four largest moons. For each moon they deduce the radius $r$ of its circular orbit around Jupiter and its orbital period $T$ . Their results are:

Moon	$r$ / $10^{8}$ m ± $0.2 \times 10^{8}$ m	$T$ / days ± 0.01 days
Io	4.2	1.77
Europa	6.8	3.55
Ganymede	10.6	7.15
Callisto	19.0	16.70

(a)
Show that, for moons in circular orbits around a planet of mass $M$ , $T^{2} = \frac{4 π^{2}}{G M} r^{3}$ .
2 marks
(b)
Calculate the absolute uncertainty in $r^{3}$ for Io.
2 marks
(c)
The graph shows the variation of $T^{2}$ with $r^{3}$ for the four moons, with error bars for $r^{3}$ and the line of best fit.
Outline why no error bars are shown for $T^{2}$ .
1 mark
(d)
Determine, using the graph, the mass of Jupiter.
3 marks
(e)
Discuss the choice of a graph of $T^{2}$ against $r^{3}$ for these data.
2 marks

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Question 6 · PHY-00226Paper 2 · HL only · 20 marks

A rover on the surface of Mars launches a small sample capsule of mass 0.50 kg from a level plain. The capsule leaves the launcher at ground level with a speed of $42 {m s}^{- 1}$ at $50^{\circ}$ above the horizontal.

The following data are given:

mass of Mars $= 6.42 \times 10^{23} kg$
radius of Mars $= 3.39 \times 10^{6} m$

The atmosphere of Mars is very thin. Ignore air resistance unless a part says otherwise.

(a)
Show that the gravitational field strength at the surface of Mars is about $3.7 {N kg}^{- 1}$ .
2 marks
(b)(i)
Calculate the time of flight of the capsule.
2 marks
(b)(ii)
Calculate the horizontal distance travelled by the capsule.
2 marks
(b)(iii)
Calculate the maximum height reached by the capsule.
2 marks
(c)
The same launcher is used on Earth, with the same launch speed and angle. Determine the ratio $\frac{horizontal distance on Mars}{horizontal distance on Earth}$ . Ignore air resistance on Earth.
2 marks
(d)
Explain, without calculation, why the capsule lands with the same speed as it was launched.
2 marks
(e)(i)
A later mission must send a sample capsule away from Mars completely. Show that the escape speed from the surface of Mars is about $5 {km s}^{- 1}$ .
2 marks
(e)(ii)
Calculate the minimum energy needed to move the 0.50 kg capsule from the surface of Mars to infinity.
2 marks
(e)(iii)
Outline why the escape speed does not depend on the direction in which the capsule is launched.
1 mark
(f)
Radio signals from the rover travel to Earth at the speed of light. On one day the distance between Mars and Earth is $2.25 \times 10^{11} m$ . Calculate the time taken for a signal from the rover to reach Earth.
1 mark
(g)
The thin atmosphere of Mars does exert a small drag force on the capsule. Predict how the horizontal distance and the speed on landing compare with your answers to (b)(ii) and (d).
2 marks

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