Weight, Mass and Gravitational Field Strength
Understanding Weight, Mass and Gravitational Field Strength
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Weight is the force exerted on an object due to gravity. It depends on the mass of the object and the gravitational field strength where the object is located.
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Mass is a measure of the amount of material in a body. It is a scalar quantity, meaning it only has magnitude and no direction.
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Gravitational field strength is a measure of the force of gravity in a particular location. On Earth, the gravitational field strength is approximately 9.8 N/kg.
Weight and Gravity
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The weight of an object can be calculated using the formula w = m * g, where w is weight, m is mass and g is gravitational field strength.
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As weight is a force, it is measured in newtons (N).
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The weight of an object will change if it goes to a place where the gravitational field strength is different; for example, an object will weigh less on the Moon than on the Earth.
Mass and its Properties
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Mass does not change with location. Even if an object is taken to the Moon or a distant planet, its mass remains the same.
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Mass is measured in kilograms (kg).
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The inertial mass of an object is a measure of how hard it is to change the object’s velocity.
Gravitational Field Strength
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On Earth, the gravitational field strength is around 9.8 N/kg. This means that for every kilogram of mass an object has, a force of 9.8 newtons is acting on it due to gravity.
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Gravitational field strength varies slightly across the surface of the Earth, but for most calculations, it can be taken as a constant 9.8 N/kg.
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On other planets or moons, the gravitational field strength is different. For example, on the Moon, it’s only about 1.6 N/kg.
Weight vs Mass
- Weight and mass are not the same thing. Weight is a force and depends on the local value of gravity, whereas mass is a measure of the amount of matter in an object and is the same everywhere.