free-body diagrams free-body diagrams are pictures that show the size and direction of all forces...
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Free-body diagramsFree-body diagrams
Free-body diagrams are pictures that show the size and direction of all forces acting on an object.
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Steps to drawing a free body diagram
1.Pick one object to analyze
2.Draw a box to represent the object
3.Draw an arrow to represent each force acting on the object
4.Make sure the arrow shows the direction and relative size of the force
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Problem 1Problem 1
A book is at rest on a table top. Diagram the forces acting on the book.
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Problem 1Problem 1
In this diagram, there are normal and gravitational forces on the book.
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Problem 1Problem 1
The forces are balanced (they cancel each other out)
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Problem 2Problem 2
An egg is free-falling from a nest in a tree. Neglect air resistance. Draw a free-body diagram showing the forces involved.
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Problem 2Problem 2
Gravity is the only force acting on the egg as it falls.
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Problem 2Problem 2
The forces are unbalanced, so the egg will accelerate downward.
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Problem 3Problem 3 A flying squirrel is gliding (no wing flaps)
from a tree to the ground at constant velocity. Consider air resistance. A free body diagram for this squirrel looks like…
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Problem 3Problem 3
Gravity pulls down on the squirrel while air resistance keeps the squirrel in the air for a while.
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Problem 4Problem 4
A rightward force is applied to a book at rest, in order to move it across a desk. Consider frictional forces. Neglect air resistance. Construct a free-body diagram for the book.
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Note the applied force arrow pointing to the right. Notice how friction force points in the opposite direction. Finally, there are still gravity and normal forces involved.
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Problem 5Problem 5
A skydiver is falling with a constant velocity. Consider air resistance. Draw a free-body diagram for the skydiver.
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Gravity pulls down on the skydiver, while air resistance pushes up as she falls.
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Problem 6Problem 6
A man drags a sled across loosely packed snow with a rightward acceleration. Draw a free-body diagram of the forces acting on the sled.
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The rightward force arrow points to the right. Friction slows his progress and pulls in the opposite direction. Since there is not information that we are in a blizzard, normal forces still apply as does gravitational force since we are on planet Earth.
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Problem 7Problem 7
A football is moving upwards toward its peak after having been booted by the punter. Neglect air resistance. Draw a free-body diagram of the football in mid-air.
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The force of gravity is the only force described. It is not a windy day (no air resistance).
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Problem 8Problem 8
A car runs out of gas and coasts to a stop on flat ground. Draw a free body diagram of the forces acting on the car.
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Even though the car is coasting down the hill, there is still the dragging friction of the road (left pointing arrow) as well as gravity and normal forces.