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Mass, Weight and Gravity.
The acceleration of a falling object acted on by gravity only is because the force of gravity on the
object is the only force acting on it, its weight (in newtons), W= mg, where m = the mass of the object
When an object is in equilibrium, the support force on it is equal and opposite to its weight.
Therefore, an object placed on a weighing balance exerts a force on the balance equal to the weight
of the object. Thus the balance measures the weight of the object.
G is also referred to as the gravitational field strength at a given position, as it is the force of gravity
per unit mass on a small object at that position. So the gravitational field strength at the Earth's
surface is 9.81N/kg. Note that the weight of a fixed mass depends on its location. For example, the
weight of a 1kg object is 9.81N on the Earth's surface and 1.62N on the Moon's surface.
The mass of an object is a measure of its inertia, which is its resistance to a change in motion. More
force is needed to give an object certain acceleration than to give an object with less mass the same
acceleration. The scale on a top pan balance is usually calibrated for convenience in grams or