Page 6 - mechanics
P. 6
Chapter – 2 Concurrent forces in 2D
2.1 Vectors and Scalars
The magnitude of a force is characterized by a certain
number of units indicating how large the force is. The SI unit
of force is the Newton (N) while the unit of force in the US
system is the pound (Ib).
The direction of a force is defined by the line of action and
the sense of the force. Quantities that have both magnitude and
direction are referred to as vectors while quantities that have
only magnitudes are referred to as scalars.
A scalar is a quantity that is fully characterized by a
number. In this book, scalars are indicated by letters in italic
type. For example: mass m, volume V, area A, length l and time
t are all scalar quantities.
On the other hand, a vector is a quantity that is fully
described by both a magnitude and a direction. For handwritten
work, a vector is generally represented by a letter with an
arrow written over it, such as A while its magnitude is
designated | A | or simply A. In this book vectors will be
symbolized in boldface type; for example, A is used to
designate vector A and A is to designate its magnitude; | A | or
|A|. Some vector quantities frequently encountered in
16
