Mass vs Weight
Mass is the amount of matter; weight is the gravitational force on it.
About this topic
Mass is the amount of matter in an object, measured in kilograms, and it is the same everywhere. Weight is the gravitational force on it, W = mg, measured in newtons, and it depends on the local gravitational field. A 60 kg person weighs about 590 N on Earth and only about 100 N on the Moon.
Balances compare masses and give the same answer anywhere, while spring scales measure weight and would read differently on the Moon. The gravitational field strength g is about 9.8 N/kg on Earth, 1.6 on the Moon and 3.7 on Mars, and it even varies slightly with latitude and altitude. Mass also measures inertia, resisting acceleration.
Example: an astronaut with a 80 kg mass has a weight of about 784 N on Earth and about 128 N on the Moon. In orbit the astronaut feels weightless, yet still has the same mass, and it is still hard to push a heavy object in space. Shipping, cooking and engineering use mass, while structures must be designed for weight.
Common confusion: in everyday speech people say weight and give kilograms. In physics, kilograms measure mass, and newtons measure weight.
Key ideas
- W = mg
- Mass is constant everywhere
- Weight changes with gravity
Quick check
Use cases: where Mass vs Weight helps
- Homework: review the key idea behind Mass vs Weight before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Mass vs Weight without notes.
- Visual learning: play with the interactive lab to see how Mass vs Weight changes when you adjust its inputs.
- Teaching a friend: explain Mass vs Weight in your own words, then compare your version with the key ideas.
The same laws describe car crashes, sports, satellites and everyday machines.
Frequently asked questions
What is Mass vs Weight?
Mass is the amount of matter; weight is the gravitational force on it.
What will I learn in Mass vs Weight?
W = mg. Mass is constant everywhere. Weight changes with gravity.
Is Mass vs Weight part of Physics?
Yes. It is one of 150 Physics topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Mass vs Weight lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Mass vs Weight?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.