Mass and weight on Earth, the Moon and beyond
Weigh objects with a beam balance and a spring balance on Earth, the Moon, Mars and Jupiter, and see which reading changes.
Core concept
In short: Weigh things on Earth and the Moon: mass stays the same, weight changes.
Mass is the amount of matter and stays the same everywhere; weight is the pull of gravity and changes from place to place
Topic: Measurement
mass: How much matter something has, measured in grams or kilograms. It is the same everywhere. All key words is the amount of matter in an object, measured in kilograms (kg) with a beam balance, which compares the object with standard masses. weight: The pull of gravity on something, measured in newtons. It is less on the Moon. All key words is the force: A push or a pull. Forces can start, stop or turn things. All key words of gravity: The pull that makes things fall towards the Earth. All key words pulling on the object, measured in newtons (N) with a spring balance. On Earth, gravity pulls each kilogram with about 9.8 N. The Moon's gravity is about one sixth as strong, so things weigh less there, but their mass does not change. Weight = mass × gravitational field strength (W = m × g).
What you will learn
- Distinguish mass from weight.
- Use a beam balance to measure mass and a spring balance to measure weight.
- Calculate weight using W = m × g.
Before you start
- Know that gravity pulls objects towards the Earth.
Materials
- A book, a water bottle, a bag of rice and a school bag
Equipment
- Beam balance with standard masses
- Spring balance marked in newtons
Procedure
- Weigh the bag of rice on Earth with both balances and record the readings.
- Take it to the Moon and weigh it again. Which reading changed?
- Weigh a second object on Earth.
- Try Mars and Jupiter.
How this simulation is simplified
- Gravitational field strength: Earth 9.8 N/kg, Moon 1.6 N/kg, Mars 3.7 N/kg, Jupiter 24.8 N/kg (at the cloud tops).