IGCSE Physics Mass and Weight Questions and Worked Solutions (1.3) | 0625

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IGCSE Physics 0625 · Topic 1.3

IGCSE Physics Mass and Weight Questions and Worked Solutions

50 topic-wise practice questions on Mass and Weight (Unit 1: Motion, Forces and Energy), written to the Cambridge IGCSE Physics 0625 syllabus for 2026–2028, each with a step-by-step worked solution.

50 questions29 Core11 Extended10 Challenge112 marksTextbook §1.3 · pp. 25–28
Questions tagged Core are for all candidates (Papers 1 & 3). Questions tagged Extended are Supplement content (Papers 2 & 4). Questions 41–50 are harder Challenge questions. Try each question first, then tap Show solution to check your working.

Topic guide: Mass and Weight

Mass is the amount of matter in an object and is the same everywhere. Weight is the gravitational force on that mass, so it depends on the gravitational field strength where the object is.

Key formulas

W = m gweight W (N), mass m (kg), gravitational field strength g (N/kg)Core
g = W ÷ mg is weight per unit massCore
g on Earth ≈ 9.8 N/kg = 9.8 m/s²field strength equals acceleration of free fallCore

Prerequisite knowledge

  • Units: kg, g, N
  • Rearranging W = mg
  • Idea of a force (1.5)

Exam tips & common mistakes

  • Convert grams to kilograms before using W = mg
  • State mass in kg and weight in N — mixing them up loses marks
  • If asked what changes on the Moon, the answer is weight, not mass

Key facts from the syllabus (1.3)

  • Mass is measured in kilograms and does not change with location
  • Weight is a force, measured in newtons, and changes with g
  • Gravitational field strength is the force per unit mass
  • g on the Moon is about 1.6 N/kg, so objects weigh about 1/6 of their Earth weight
  • A beam balance compares masses (weights on both sides change equally); a spring balance measures weight
  • Extended weight is the effect of a gravitational field on a mass; g is numerically equal to the acceleration of free fall

Textbook: §1.3 Mass and weight, pp. 25–28

1
Core[1 mark]

State what is meant by mass.

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Method: Mass measures the quantity of matter.

The quantity of matter in an object
2
Core[1 mark]

State what is meant by weight.

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Method: Weight is a force due to gravity.

The gravitational force on an object that has mass
3
Core[1 mark]

State the unit of weight.

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Method: Weight is a force.

newton (N)
4
Core[1 mark]

Define gravitational field strength.

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Method: g = W/m.

Force per unit mass (weight per kilogram)
5
Core[2 marks]

Calculate the weight of a 65 kg student on Earth (g = 9.8 N/kg).

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Method: W = mg.

W = 65 × 9.8 = 637 N
6
Core[2 marks]

A rock has a weight of 147 N on Earth (g = 9.8 N/kg). Calculate its mass.

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Method: m = W ÷ g.

m = 147 ÷ 9.8 = 15.0 kg
7
Core[2 marks]

An astronaut of mass 80 kg stands on the Moon where g = 1.6 N/kg. Calculate her weight on the Moon.

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Method: W = mg.

W = 80 × 1.6 = 128 N
8
Core[2 marks]

The astronaut in the previous question returns to Earth. State what happens to her mass and her weight.

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Method: Mass does not depend on location; weight depends on g.

Mass stays 80 kg; weight increases (to about 784 N)
9
Core[2 marks]

A 5.0 kg object weighs 18.5 N on Mars. Calculate the gravitational field strength on Mars.

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Method: g = W ÷ m.

g = 18.5 ÷ 5.0 = 3.70 N/kg
10
Core[1 mark]

State the link between gravitational field strength and the acceleration of free fall.

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Method: Both are g.

They are numerically equal (9.8 N/kg = 9.8 m/s²)
11
Core[2 marks]

Describe how a beam balance compares the weights of two objects.

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Method: A balance is level when the forces (weights) on both sides are equal.

Place the objects on opposite pans; the balance is level when the weights (and so masses) are equal
12
Core[1 mark]

Explain why a beam balance gives the same reading on the Moon as on Earth.

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Method: Both pans are affected by the same g, so comparison is unchanged.

g acts equally on both sides, so it compares masses, which do not change
13
Core[2 marks]

A box weighs 490 N on Earth. Calculate its mass. (g = 9.8 N/kg)

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Method: m = W/g.

m = 490 ÷ 9.8 = 50.0 kg
14
Core[3 marks]

A parcel has mass 12 kg. Calculate its weight on Earth (g = 9.8 N/kg) and on Jupiter (g = 23 N/kg).

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Method: W = mg for each.

Earth: 118 N; Jupiter: 276 N
15
Core[1 mark]

State one factor that the gravitational field strength at a planet's surface depends on.

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Method: Stronger gravity for bigger mass.

The mass of the planet
16
Core[2 marks]

A bag of rice has mass 5.0 kg. Calculate its weight on Earth (g = 9.8 N/kg).

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Method: W = mg.

W = 5.0 × 9.8 = 49.0 N
17
Core[2 marks]

A student's weight is 539 N on Earth (g = 9.8 N/kg). Calculate the student's mass.

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Method: m = W ÷ g.

m = 539 ÷ 9.8 = 55.0 kg
18
Core[1 mark]

State the unit of mass.

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Method: SI unit.

kilogram (kg)
19
Core[1 mark]

State the unit of gravitational field strength.

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Method: Force per mass.

N/kg
20
Core[2 marks]

A 250 g apple is held in the hand. Calculate its weight (g = 9.8 N/kg).

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Method: Convert g to kg.

W = 0.250 × 9.8 = 2.45 N
21
Core[2 marks]

An astronaut weighs 160 N on the Moon (g = 1.6 N/kg). Calculate her mass.

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Method: m = W ÷ g.

m = 160 ÷ 1.6 = 100 kg
22
Core[2 marks]

State and explain whether the mass of a bottle of water changes when it is taken to the top of a mountain.

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Method: Mass is amount of matter.

It does not change; the amount of matter is the same
23
Core[2 marks]

A robot of mass 180 kg lands on Mars (g = 3.7 N/kg). Calculate its weight on Mars.

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Method: W = mg.

W = 180 × 3.7 = 666 N
24
Core[2 marks]

An object weighs 45 N on a planet and has mass 9.0 kg. Calculate g on that planet.

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Method: g = W ÷ m.

g = 45 ÷ 9.0 = 5.00 N/kg
25
Core[2 marks]

Describe how a top-pan balance or a spring balance can be used to compare two weights.

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Method: Measure each.

Place each object on the balance in turn and compare the readings; the larger reading is the larger weight
26
Core[1 mark]

State whether weight is a force or an amount of matter.

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Method: Definition.

A force
27
Core[2 marks]

Explain why a person's weight on the Moon is less than on Earth.

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Method: Smaller g.

The Moon's gravitational field strength is smaller, so the gravitational force on the same mass is smaller
28
Core[3 marks]

The weight of a 2.0 kg mass is measured at different places: 19.6 N, 19.5 N and 3.2 N. Calculate g for each and suggest where the last reading was taken.

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Method: g = W/m.

g = 9.80, 9.75, 1.60 N/kg; the last was taken on the Moon
29
Core[2 marks]

A mass of 0.50 kg hangs from a spring balance on Earth. State the reading (g = 9.8 N/kg).

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Method: W = mg.

4.90 N
30
Extended[2 marks]

Describe weight in terms of a gravitational field.

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Method: A mass in a gravitational field experiences a force.

Weight is the effect of a gravitational field on a mass: the force the field exerts on it
31
Extended[2 marks]

A spacecraft moves far away from the Earth. Explain what happens to the weight of an astronaut in it.

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Method: The Earth's gravitational field gets weaker with distance.

Weight decreases because g decreases with distance from Earth; mass is unchanged
32
Extended[3 marks]

An object of mass 2.0 kg is dropped on a planet and accelerates at 3.7 m/s² with no air resistance. Calculate its weight there.

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Method: Acceleration of free fall = g, so W = mg.

W = 2.0 × 3.7 = 7.40 N
33
Extended[2 marks]

A spring balance and a beam balance are taken to the Moon. State which reading changes and why.

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Method: Spring balance measures force (weight); beam balance compares masses.

The spring balance reading decreases because it measures weight, which depends on g
34
Extended[2 marks]

An object weighs 30 N on Earth (g = 9.8 N/kg). Calculate its weight on a planet where g = 3.7 N/kg.

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Method: Find m, then W = mg.

m = 30 ÷ 9.8 = 3.06 kg; W = 3.06 × 3.7 = 11.3 N
35
Extended[2 marks]

Explain why all objects fall with the same acceleration in a vacuum, whatever their mass.

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Method: g = W/m is the same.

Weight is proportional to mass, so W/m = g is the same for all objects; with no air resistance the acceleration is g
36
Extended[2 marks]

State the acceleration of a falling object on the Moon if g = 1.6 N/kg and there is no atmosphere.

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Method: a = g.

1.6 m/s²
37
Extended[3 marks]

An object is dropped from rest on a planet and reaches 11.1 m/s after 3.0 s (no air resistance). Calculate g on the planet and the weight of a 4.0 kg mass there.

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Method: g = a = Δv/Δt.

g = 11.1 ÷ 3.0 = 3.70 N/kg; W = 4.0 × 3.7 = 14.8 N
38
Extended[2 marks]

Describe the gravitational field around the Earth.

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Method: Field lines into Earth's centre.

A region where masses experience a force towards the Earth's centre; the field gets weaker further away
39
Extended[3 marks]

A satellite of mass 500 kg is at a height where g = 8.7 N/kg. Calculate the gravitational force on it and compare it with its weight at the surface (g = 9.8 N/kg).

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Method: W = mg.

At height: 4350 N; at surface: 4900 N; it is smaller at height
40
Extended[2 marks]

A mass of 3.0 kg weighs 29.4 N. Calculate the acceleration it would have if dropped with no air resistance.

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Method: a = W/m.

a = 29.4 ÷ 3.0 = 9.80 m/s²

Challenge questions

Harder, multi-step questions at the top end of the exam. Attempt these once you are confident with the questions above.

41
ChallengeCore[4 marks]

An astronaut with a total mass of 120 kg (including suit) weighs 1176 N on Earth. On planet X the same astronaut weighs 444 N. Calculate g on Earth and on planet X, and the ratio of the weights.

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Method: g = W/m.

g(Earth) = 9.80 N/kg; g(X) = 3.70 N/kg; ratio = 2.65
42
ChallengeCore[4 marks]

A spring balance reads 7.35 N on Earth (g = 9.8 N/kg) for a rock sample. On the Moon (g = 1.6 N/kg), calculate the reading of the spring balance and the mass read by a beam balance.

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Method: Find mass first.

m = 0.750 kg; spring balance = 1.20 N; beam balance = 0.75 kg
43
ChallengeCore[3 marks]

A lunar lander has a mass of 15 000 kg. Calculate the difference between its weight on Earth (g = 9.8 N/kg) and on the Moon (g = 1.6 N/kg).

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Method: ΔW = mΔg.

ΔW = 15000 × 8.2 = 123000 N
44
ChallengeCore[4 marks]

A bag of flour labelled 1.00 kg is weighed on a newton meter at a place where g = 9.78 N/kg and at another where g = 9.83 N/kg. Calculate both readings and explain why its mass label is still correct.

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Method: W = mg.

9.78 N and 9.83 N; mass is the same everywhere — only the gravitational field strength differs
45
ChallengeCore[3 marks]

Explain why a beam balance on the Moon still balances a 1 kg mass against a 1 kg standard, even though both weigh less than on Earth.

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Method: Same g on both pans.

Both pans are in the same gravitational field, so both weights are reduced by the same factor and still balance
46
ChallengeExtended[4 marks]

A 2.0 kg object is dropped on a planet where g = 3.7 N/kg (no atmosphere). Calculate (a) its weight, (b) its acceleration, (c) its speed after 4.0 s.

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Method: a = W/m = g.

(a) 7.40 N (b) 3.70 m/s² (c) 14.8 m/s
47
ChallengeExtended[4 marks]

A probe falls freely from rest near a moon and reaches 6.0 m/s after 2.5 s. Its mass is 300 kg. Calculate the moon's gravitational field strength and the probe's weight there.

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Method: g = Δv/Δt.

g = 2.40 N/kg; W = 720 N
48
ChallengeExtended[3 marks]

Explain why the gravitational field strength in a spacecraft orbiting Earth is not zero, even though astronauts feel weightless.

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Method: Field still present.

The Earth's field is still strong there (only slightly weaker); astronauts feel weightless because they and the craft fall together in orbit
49
ChallengeExtended[4 marks]

A 50 kg student stands on scales in a lift. The lift accelerates upwards at 1.2 m/s². Calculate the reading on the scales (g = 9.8 N/kg) and explain why it differs from the student's weight.

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Method: R − mg = ma.

R = 50 × (9.8 + 1.2) = 550 N; extra force is needed to give the upward acceleration
50
ChallengeExtended[4 marks]

The same 50 kg student is in a lift accelerating downwards at 1.2 m/s². Calculate the scale reading and state what the reading would be if the cable broke.

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Method: mg − R = ma.

R = 50 × 8.6 = 430 N; zero in free fall
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