Lesson 1 of 6

Mass and weight

Goal: Tell mass from weight.

Puzzles for this lesson

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An astronaut standing on the grey, dusty surface of the Moon. The Earth is small in the black sky

Mass is the amount of matter in an object. Weight is the pull of gravity on it.

MassMeasured in kilograms (kg)
WeightA force, so it is measured in newtons (N)
  • Mass stays the same wherever you go. It only changes if matter is added or taken away.
  • Weight depends on where you are. The Moon’s gravity is weaker than the Earth’s, so everything weighs less there.
  • On the Earth, weight pulls towards the centre of the Earth. That direction is what we call down.

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Key words in this lesson

Mass The amount of matter in an object, measured in kilograms

Weight The force of gravity on an object, measured in newtons

Gravity A force that pulls any two objects towards each other

For teachers: AQA 3.1.2 · Pearson Edexcel 39.5 · Cambridge 7Pf.03 in part