← ⚛️ Physics · usually met in Std 6-9

Weight and mass

Mass is how much matter a thing contains. Weight is the force gravity exerts on that mass. Everyday speech confuses them; physics cannot afford to.

Mass is measured in kilograms and does not change wherever you take it. Weight is a force, measured in newtons, and it depends on the local strength of gravity. A 50 kg student has a mass of 50 kg on the Earth, on the Moon and in orbit — but weighs about 490 newtons on Earth, about 81 on the Moon, and is effectively weightless in free fall.

This is why astronauts float. They are not beyond gravity — at the space station's height the Earth's pull is still almost as strong as it is on the ground. They are falling, continuously, along with their spacecraft, and when everything around you falls at the same rate there is nothing to press against.

Worth knowing

A kitchen scale really measures force and then does the division for you, assuming it is on the Earth.
A beam balance compares masses and gives the same answer anywhere, which is why it is the more honest instrument.
Weight varies slightly across the Earth: you weigh a little less at the equator than at the poles.

Want to see it moving? Search YouTube for “Weight and mass” ↗ — we send you to the search rather than to one video, because a link to one video eventually rots.

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This entry was written for Star Student in our own words — it is a summary, not a source. Here is where the people who actually hold these facts keep them. Go and check.

Your own textbook ↗Balbharati publishes the textbooks free to read online. Your chapter is the thing to check first — an encyclopedia is a summary, and the syllabus is the syllabus.

Last gone through: 1 October 2026 · How these entries are written

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Weight and mass

Worth knowing

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🧭 Do not take our word for it