The key difference between mass and weight is that mass is a measure of how much matter an object contains, while weight is the force of gravity acting on that mass.
Mass vs. Weight: A Detailed Comparison
To understand the difference between mass and weight, consider the following aspects:
| Feature | Mass | Weight |
|---|---|---|
| Definition | Amount of matter in an object. | Force of gravity acting on an object's mass. |
| Nature | Scalar quantity (magnitude only) | Vector quantity (magnitude and direction) |
| Measurement | Measured in kilograms (kg) or grams (g). | Measured in Newtons (N). |
| Change | Remains constant regardless of location. | Varies depending on gravitational force. |
| Zero Value | Cannot be zero. | Can be zero (e.g., in freefall). |
| Effect of Gravity | Independent of gravity. | Directly proportional to gravity. |
| Formula | Basic property of matter | Weight (W) = Mass (m) x Acceleration due to gravity (g) or W = mg |
Key Differences Explained
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Mass: Think of mass as the 'stuff' that makes up an object. A brick, for example, has a certain amount of 'stuff' in it, regardless of whether it's on Earth or on the Moon. That 'stuff' is the mass.
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Weight: Weight, on the other hand, is the force with which gravity pulls that 'stuff' downwards. Because the Moon's gravity is weaker than Earth's, the brick will weigh less on the Moon, even though its mass remains the same.
Examples to Illustrate the Difference
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On Earth vs. Moon: An object with a mass of 10 kg will have a weight of approximately 98 N on Earth (assuming g = 9.8 m/s²). However, on the Moon, where the gravity is about 1/6th of Earth's, the same object will weigh only about 16.3 N. The mass remains 10 kg in both locations.
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In Freefall: An astronaut in the International Space Station is essentially in freefall. Although they still have mass, they experience weightlessness because they are constantly falling towards the Earth (along with the space station). Effectively, their apparent weight is close to zero.
Summary
Mass is an inherent property of an object that measures its resistance to acceleration, while weight is the gravitational force exerted on that object and is dependent on the gravitational field. Mass is constant, while weight can change depending on location and gravitational pull.
