Vectors and Scalars

Essentially all of the quantities we encounter in Physics -- certainly all that we will see in this course -- may be classified as scalars or vectors.

Scalars

A quantity is a scalar if it is fully specified by a number and a unit. A few examples are

mass

1.23 kg

temperature

37o C or 99o F

time

75 minutes

energy

2.34 joules

volume

5.43 m3

However, some quantities require more information.

Vectors

A quantity is a vector if it is fully specified by a number, a unit -- and a direction. A few examples are

displacement

5.3 km, due North

velocity

2.34 m/s, 30o W of N

acceleration

9.8 m/s2, downward

momentum

1.234 kg-m/s, to the right

electric field

6.7 N/C, 60o E of N

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(C) 2003, Doug Davis; all rights reserved