Transcript 5.2 Vectors and Scalars

Mechanics
Unit 5: Motion and Forces
5.2 Vectors and Scalars
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Fundamentals of physics - Mechanics
Vectors and Scalars
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A vector quantity is one that has
magnitude (size) and direction.
Velocity, force, acceleration, and
momentum are vector quantities.

A
scalar quantity only has
magnitude alone.
Speed, time, temperature, and
energy are some examples of
scalar quantities.
A distance sm
is a scalar but a
displacement
xm to the east
is a vector.
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Fundamentals of physics - Mechanics
Vectors and Scalars
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Vector quantities may be
represented by arrows.

The magnitude of the vector
quantity is represented by the
length of the direction by the
arrowhead.

An arrow drawn to scale and
pointing in the appropriate
direction represents a vector.
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Fundamentals of physics - Mechanics
Adding Vectors
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Consider the forces F1 and
F2 acting on a body in the
directions shown in the
diagram.
 The resultant Fr is the
diagonal of the
parallelogram.
 When the
vectors are
90o apart
then the
parallelogram
becomes a
rectangle.

A displacement of 12m
North followed by 5m East.
Resultant
displacement
is 13m at a
bearing of
22.6o.
Fundamentals of physics - Mechanics
Vectors and Scalars
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The weight of a wheel rolling down an inclined plane can
be considered as the resultant of two forces – S (parallel
to the plane) and D perpendicular to the plane.
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Fundamentals of physics - Mechanics
Vectors and Scalars
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Would a wheelbarrow sink deeper when it is pushed or
pulled over soft soil?
 Answer: Consider the effort F applied on the wheel by
the person. If F points downward (pushing) then the
component Fd adds to the weight of the wheelbarrow and
when the effort is applied upward it subtracts from the
weight. Thus in pushing the net force on the wheels is
greater.
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