Unformatted text preview: 12/8/2018 Vector Nature of Forces | Boundless Physics Boundless Physics
The Laws of Motion Vector Nature of Forces 1/5 12/8/2018 Vector Nature of Forces | Boundless Physics Forces in Two Dimensions
Forces act in a particular direction and have sizes dependent upon how
strong the push or pull is. LEARNING OBJECTIVES Explain why forces are classi ed as “vector quantities” KEY TAKEAWAYS Key Points When determining what happens when two forces act
on the same object, it is necessary to know both the
magnitude and the direction of both forces to calculate
the result.
When two forces act on a point particle, the resulting
force or the resultant (also called the net force ), can be
determined by following the parallelogram rule of
vector addition.
Free-body diagrams can be used as a convenient way
to keep track of forces acting on an object.
Key Terms vector: A directed quantity, one with both magnitude and direction; the between two points.
free-body diagram: A free body diagram, also called a force diagram, is a pictorial representation often used
by physicists and engineers to analyze the forces acting
on a body of interest. 2/5 12/8/2018 Vector Nature of Forces | Boundless Physics resultant: A vector that is the vector sum of multiple vectors Forces act in a particular direction and have sizes dependent upon how
strong the push or pull is. Because of these characteristics, forces are
classi ed as “vector quantities. ” This means that forces follow a di erent
set of mathematical rules than physical quantities that do not have
direction (denoted scalar quantities).
For example, when determining what happens when two forces act on
the same object, it is necessary to know both the magnitude and the
direction of both forces to calculate the result. If both of these pieces of
information are not known for each force, the situation is ambiguous. For
example, if you know that two people are pulling on the same rope with
known magnitudes of force but you do not know which direction either
person is pulling, it is impossible to determine what the acceleration of
the rope will be. The two people could be pulling against each other as
in tug of war or the two people could be pulling in the same direction. In
this simple one-dimensional example, without knowing the direction of
the forces it is impossible to decide whether the net force is the result of
adding the two force magnitudes or subtracting one from the other.
Associating forces with vectors avoids such problems.
When two forces act on a point particle, the resulting force or the
resultant (also called the net force) can be determined by following the
parallelogram rule of vector addition: the addition of two vectors
represented by sides of a parallelogram gives an equivalent resultant
vector which is equal in magnitude and direction to the transversal of the
parallelogram. The magnitude of the resultant varies from the di erence
of the magnitudes of the two forces to their sum, depending on the
angle between their lines of action.
Free-body diagrams can be used as a convenient way to keep track of
forces acting on a system. Ideally, these diagrams are drawn with the
angles and relative magnitudes of the force vectors preserved so that
graphical vector addition can be done to determine the net force. 3/5 12/8/2018 Vector Nature of Forces | Boundless Physics x Forces as Vectors: Free-body diagrams of an object on a at surface and an
inclined plane. Forces are resolved and added together to determine their
magnitudes and the net force. Previous Next 4/5 12/8/2018 Vector Nature of Forces | Boundless Physics 5/5 ...
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