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Free Body Diagram
•Definition - A diagram that shows every force acting
on an object.
•Example: A book at rest on a table.
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Rules
•Isolate the object.
•Choose a coordinate system.
•Sketch the forces.
•Resolve the forces into components(If necessary).
•Find the net force.
•Apply Newton’s Second Law of Motion.
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Isolate the object
•Simplify the model just to include the object being
observed.
=
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Sketch the forces
•In this case we chose the y-axis of the coordinate
system.
•Forces stem from the center of the object outward.
•Length of the arrow represents magnitude of force.
•Direction of arrow represents direction of force.
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Find the net force.(continued)
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Try This
•A 2,200 kg car is accelerating at 1.25 m/s2 rightward
on a horizontal road. It is encountering a frictional
force of 500 N. Draw a free body diagram for the car.
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Isolate the object.
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Sketch the forces
•Note that FA is longer than FF due to the fact the car
is accelerating rightward.
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Find the net force.
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Apply Newton’s Second Law of
Motion.
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