Mass vs weight
Could you jump higher on the Moon, even though you are still just as big?
Play
Explain
You are still you on the Moon.
But you would feel very light.
Mass is how much stuff is in you. It stays the same wherever you go.
Weight is the force of gravity pulling on you. It changes depending on where you are.
The Moon has weaker gravity than Earth, so you would weigh about a sixth as much.
Mass is measured in kilograms. Weight is a force, so it is measured in newtons.
W = m × g, where g is the gravitational field strength in N/kg.
Worked example: a 30 kg child on Mars weighs 30 × 3.7 = 111 N. On Earth they weigh 30 × 9.8 = 294 N.
- Mass stays the same
- Gravity changes by world
- Weight changes with it
Want the full story?
Bathroom scales are marked in kilograms, but they really measure force and then divide by 9.8. On the Moon, they would give the wrong mass. In everyday speech, people say weight when they mean mass. Jupiter has no solid ground, so its value is for the tops of its clouds.
The Formula
weight = mass × gravity
- the weight, which is a force, measured in newtons (N)
- the mass, measured in kilograms (kg)
- the strength of gravity where you are, measured in newtons per kilogram (N/kg)
Try the numbers
Weight: 294 N
Try it at home
You need bathroom scales, a calculator.
You need: bathroom scales, a calculator.
Stand on scales. Now pretend you are on the Moon!
- Find your mass in kilograms.
- Multiply by 9.8 to get your weight on Earth.
- Multiply your mass by 1.6 for the Moon, and 24.8 for Jupiter.
What's happening: your mass stays the same, so your weight only depends on the world you are standing on.
Physics is life
Your body
Your legs carry your weight.
Daily life
Shops sell food by mass.
Nature
Whales are held up by water.
Space
You would feel light on the Moon.
Quick check
Question 1 of 3
Words to know
Weight: The force of gravity pulling on you. It is measured in newtons.