Lesson 2 of 6

Calculating weight

Goal: Calculate weight from mass.

Puzzles for this lesson

Gravitational field strength, g, tells you how hard gravity pulls on each kilogram. Multiply a mass by g to find its weight.

weight (N) = mass (kg) × g (N/kg)

On the Earth, g is about 10 N/kg. Every kilogram weighs about 10 N.
On the Moon, g is 1.6 N/kg. You would weigh about a sixth of your weight on the Earth.
g is different on every planet and moon. Your mass stays the same on all of them. Only your weight changes.

Worked example. A dog has a mass of 20 kg. On the Earth, its weight = 20 kg × 10 N/kg = 200 N. On the Moon, its weight = 20 kg × 1.6 N/kg = 32 N.

Your turn

This lesson’s activity starts here in a moment.

I can use weight = mass × g.I can compare my weight on Earth and on the Moon.

This lesson on one page. Tap it to make it bigger.

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

Gravitational field strength The force of gravity on each kilogram, in N/kg

Planet A large ball of rock or gas that orbits a star

For teachers: AQA 3.1.2 · Pearson Edexcel 40.2, 40.3