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17
Unit 1.3-1.8: Dynamics (Motion,Forces, Moments, Energy,
Work and Power)
Topic 1.3: Mass and Weight
What is mass?
Mass is a measure of the quantity of matter in an object, relative to an
observer.
It is sometimes also referred to as the resistance to motion of an object.
Mass is measured in kilograms or kg.
The mass and weight of an object are NOT the same property.
Weight and Gravitational Field Strength
The weight of an object is the gravitational force that acts on it.
It is measured in Newtons(N).
Hence, the weight of an object can change depending on the gravitational
field strength of a mass.
The gravitational field strength is defined as the force of gravity per unit
mass.
It is defined by the equation g=W/m, where g = gravitational field strength,
W = weight/force of gravity, and m = mass.
g is also equivalent to the acceleration of free fall of the planet in question.
Any object in free fall in a vacuum will fall with the same acceleration g.