1. Definition
- Mass: Mass is the amount of matter in an object. It’s a measure of how much "stuff" an object contains, independent of its location or environment.
- Weight: Weight is the force exerted by gravity on an object’s mass. It depends on both the object’s mass and the gravitational field strength of the location.
2. Nature
- Mass: A scalar quantity, meaning it has only magnitude (e.g., 5 kg).
- Weight: A vector quantity, as it has both magnitude and direction (downward, toward the center of gravity).
3. Units
- Mass: Measured in kilograms (kg), grams (g), or other units of mass in the metric system.
- Weight: Measured in newtons (N) in the SI system, as it is a force. However, weight is often expressed in kilograms-force or pounds in everyday use, which can cause confusion.
4. Dependence on Gravity
- Mass: Constant and does not change regardless of location (e.g., on Earth, the Moon, or in space).
- Weight: Varies depending on the gravitational field. For example:
- On Earth (gravity ≈ 9.8 m/s²), a 10 kg object weighs ~98 N.
- On the Moon (gravity ≈ 1/6th of Earth’s), the same object weighs ~16.3 N.
5. Measurement Tools
- Mass: Measured using a balance (e.g., a beam balance or electronic balance), which compares the object to standard masses.
- Weight: Measured using a spring scale or similar device that measures the force exerted by gravity.
6. Physical Representation
- Mass: Represents an object’s inertia (resistance to acceleration). More mass means it’s harder to move or stop the object.
- Weight: Represents the gravitational pull on the object, which determines how heavy it feels.
Example for Clarity
- A 10 kg object has the same mass on Earth, the Moon, or in space.
- Its weight, however, is:
- ~98 N on Earth.
- ~16.3 N on the Moon.
- 0 N in deep space (no gravity).
Summary Table
| Property | Mass | Weight |
|---|---|---|
| Definition | Amount of matter | Force due to gravity |
| Type | Scalar | Vector |
| Units | Kilograms (kg), grams (g) | Newtons (N) |
| Depends on | Intrinsic (constant) | Gravity (varies by location) |
| Measured by | Balance | Spring scale |
| Example | 10 kg everywhere | 98 N on Earth, 16.3 N on Moon |
