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Acceleration, Weight and Mass. Weight. Near the surface of the Earth, the pull of gravity on a body is practically constant and every falling body acquires constant acceleration equal to “g” The force that accelerates the body downward is equal to its weight “ w ”.
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Weight • Near the surface of the Earth, the pull of gravity on a body is practically constant and every falling body acquires constant acceleration equal to “g” • The force that accelerates the body downward is equal to its weight “w”
It follows that if “m” is the mass of the body, then Newton’s 2nd law equation, F = ma can be restated as: • This enables us to compute the weight of a body from its mass, or the mass of the body from its weight.
“g” can also be calculated for another planet by the equation:
Gravitational v. Inertial Mass • Obtaining a mass measurement based on the pull of gravity on a body is known as gravitational mass.
Is gravity needed to measure mass? • If some known force is applied to a body, and its acceleration is measured, we can calculate the mass using Newton’s 2nd law. • Since the amount of mass is related to body’s inertia, an how much it resists a change in motion, it is called the inertial mass.