Mass and weight are related concepts but are fundamentally different:
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Mass:
- Definition: Mass is the measure of the amount of matter in an object. It is a scalar quantity and does not change regardless of location.
- Units: The standard unit of mass in the International System of Units (SI) is the kilogram (kg). Other units include grams (g) and metric tonnes (t).
- Characteristics: Mass is an intrinsic property of an object; it remains constant regardless of the object's environment. It is a measure of inertia, meaning how much force is required to change the object's motion.
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Weight:
- Definition: Weight is the force exerted on an object due to gravity. It is a vector quantity, which means it has both magnitude and direction (toward the center of the gravitational source).
- Units: The standard unit of weight in the SI system is the newton (N), which is derived from mass (kg) multiplied by the acceleration due to gravity (approximately 9.81 m/s² on Earth). Weight can also be expressed in pounds (lbs) in the imperial system.
- Characteristics: Weight can change depending on where an object is located because it is dependent on the local gravitational field strength. For example, an object will weigh less on the Moon than on Earth due to the Moon's weaker gravity.
In summary, mass is a measure of how much matter there is in an object and remains constant, while weight is the force that results from gravity acting on that mass and can vary depending on the gravitational environment.