What is the Difference Between Mass and Weight?
Mass measures how much matter an object contains, while weight measures the force of gravity pulling on that mass. They're related but not the same — your mass stays constant everywhere, but your weight changes depending on gravity.
Mass (kg) is the amount of matter in an object and stays constant. Weight (N) is the gravitational force on that mass, given by W = m·g, so it changes with the local gravitational field g.
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Step-by-step worked examples
A person has a mass of 60 kg on Earth (g = 9.8 m/s²). Find their weight.
W = m·g = 60 × 9.8 = 588 N
An astronaut has a mass of 80 kg. What is their weight on the Moon (g = 1.62 m/s²)?
W = m·g = 80 × 1.62 = 129.6 N
A 10 kg object — find its weight on Earth and on Mars (g_Mars = 3.71 m/s²).
Earth: W = 10 × 9.8 = 98 N Mars: W = 10 × 3.71 = 37.1 N
Flashcards
Quick quiz
Q1.A 50 kg object on Earth (g = 9.8 m/s²) weighs...
Q2.Which quantity stays the same on the Moon and on Earth?
Q3.What is the unit of weight?
Q4.An object's mass is 20 kg. What is its weight on Mars (g = 3.71 m/s²)?
The full card deck, worked steps and AI-tutor support for “What is the Difference Between Mass and Weight?” are in Notek — study by hand before your exam.
Common mistakes
Mass and weight are the same thing. — Correct: Mass (kg) is matter content; weight (N) is the gravitational force on that mass — they differ.
A bathroom scale measures mass directly. — Correct: It measures weight (force) and converts it to a mass reading assuming Earth's standard g.
Weight is constant everywhere in the universe. — Correct: Weight changes with local gravity — the same object weighs less on the Moon.
Kilograms measure weight. — Correct: Kilograms measure mass; newtons measure weight (force).
FAQ
What is mass vs weight?
Mass is the amount of matter in an object (kg); weight is the gravitational force on that mass (N).
What is the weight formula?
W = m·g, where m is mass in kg and g is gravitational acceleration in m/s².
What are examples of mass and weight?
A 70 kg person has constant mass everywhere but weighs about 686N on Earth and only 113N on the Moon.
How to calculate weight from mass?
Multiply the mass by the local gravitational acceleration: W = m × g.