Mass and Weight
Mass is the amount of matter in an object, while weight is the gravitational force acting on that mass.
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Mass is the amount of matter in an object, while weight is the gravitational force acting on that mass.
- Weight equals mass times gravitational field strength
- Mass is in kilograms and weight in newtons
- Weight changes with location, mass does not
🧠 Quick quiz
Three questions. Score 2 or more to complete the topic.
What is Mass and Weight?
Within Physics, which covers forces, energy, waves, electricity, magnetism, light and space explained through motion and experiments, this topic explains Mass and Weight. Physics topics explain how things move, push, heat up and carry energy, so each one here pairs a definition with a live model you can change.
Check that you can explain Mass and Weight in your own words and give one example from everyday life. If you can do that, you have understood the core idea.
Understanding Mass and Weight explains how the physical world behaves, from sport and transport to electricity and medicine.
Mass and Weight in detail
Mass is the amount of matter in an object, measured in kilograms, and it is the same everywhere. Weight is the gravitational force on the object, measured in newtons: W = mg. On Earth g is about 9.8 N/kg, so a 60 kg person weighs about 590 N, while on the Moon (g ≈ 1.6 N/kg) the same person weighs about 100 N.
Mass is measured with a balance and weight with a newtonmeter or spring balance. Mass is a scalar and weight is a vector pointing toward the centre of the planet. Mixing up the two is a common error in everyday language.
How the interactive helps you understand Mass and Weight
Watch the force arrows in the interactive. Use any sliders or buttons it offers to change the values and see how the force arrows responds.
Before you change anything, predict the result. Then change one value at a time and check whether your prediction was right. This is a quick way to build a correct mental model of Mass and Weight.
Real-life uses and examples
- Answer “explain” questions by linking Mass and Weight to a clear cause and effect.
- Predict what a ball, car or circuit will do with Mass and Weight before you do the calculation.
- Explain everyday devices, such as brakes, lifts or chargers, using Mass and Weight.
Common mistakes to avoid
- Forgetting that some quantities, such as force or velocity, also have a direction.
- Mixing up Mass and Weight with a related quantity that has different units.
- Learning the definition without testing it. Use the quiz and the interactive to check that you can apply the idea.
Frequently asked questions about Mass and Weight
What is Mass and Weight?
Mass is the amount of matter in an object, while weight is the gravitational force acting on that mass.
What are the most important points about Mass and Weight?
The main points are: Weight equals mass times gravitational field strength; Mass is in kilograms and weight in newtons; Weight changes with location, mass does not.
Why is Mass and Weight useful?
Understanding Mass and Weight explains how the physical world behaves, from sport and transport to electricity and medicine.
How can I practise Mass and Weight?
Open the interactive at the top of this page and change the controls one at a time. Predict the result before each change, then take the three-question quiz. A score of two or more marks the topic as complete on this device.
Which topics are related to Mass and Weight?
Related topics in Physics include Resultant Forces, Hooke's Law and Springs, Atmospheric Pressure.