Physics Practice Worksheet
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SOLUTIONS (see below)
The Gravitational Force (Fgrav) Commonly known as Weight
Working Problems Involving Fgrav = m g
In an earlier lab we measured the acceleration of gravity, g: the characteristic acceleration that falling bodies
typically experience at the Earth's surface. The tremendous gravitational field of planet Earth is responsible
for the gravitational force that causes this acceleration--a force that, unless it is balanced by a support or other
force, causes objects to fall. This gravitational force--commonly known as an object's weight--is always
present here at Earth's surface. It is found using F= ma: replacing the acceleration with g. So the recipe for
computing an object's weight (in Newtons) at Earth's surface is to multiply its mass in kg by g=9.80 m/sec2.
I. Defining the variables:
the variable and brief description
symbol
units
notes
Fgrav: gravitational force on the object
Fgrav
Newtons (N)
weight varies w/ location in universe
mass: the mass of the object
m
kilograms (kg) mass same independent of location
the acceleration of gravity
g
m /sec2
at Earth's surface g= 9.80 m/sec2
note: An important conversion factor between force units: 1 pound (lb) = 4.45 Newtons (N)
II. The Key Equations:
equation 1
Fgrav= m g (weight = mass multiplied by acceleration of gravity)
equation 2
m = Fgrav / g (mass = weight divided by acceleration)