Figure 1 Coordinate system

Figure 2.1

Coordinate system
Here in this chapter we will consider two coordinate systems: Cartesian coordinate system and Polar coordinate system.
In Physics, for most applications and explanations, it is necessary to speci­fy the locations of objects. For instance, the description of the motion of a car, an airplane in the sky, a ship on the ocean, or an object anywhere require a meth­od for describing the position of them. Locating an object in space is accom­plished by means of a system of coordinates.
The Cartesian plane is formed by using two lines intersecting at right angles, as shown in Figure 2.1. The horizontal line is usually called the x-axis, and the vertical line is usually called the y-axis. The point of intersection of these two axes is the origin, and the two axes divide the plane into four parts called quadrants. The x-axis contains positive numbers to the right of the origin and negative numbers to the left of the origin. The y-axis contains positive numbers above the origin and negative numbers below the origin.
In Figure 2.1, the point P is given as (3,2). This means that, to reach to the point from origin, move 3 units along the pos­itive x-axis and then 2 units along the positive y-axis.
Vector. Vector components
Every physical quantity can be classified as either a scalar or a vector quantity. A scalar is a quantity that can be completely described by a number (called its magnitude) and a unit. Examples of scalars are length, temperature, and volume.
A vector is a quantity that requires both magnitude(size) and direction to be completely described. Examples of vectors are force, displacement, and velocity. To completely describe a force, you must give not only its magnitude (size or amount), but also its direction.
Displacement is the net change in position of an object, or the direct distance and direction it moves.
We can add, subtract vectors and multiplying or dividing a Vector by a Scalar.
Vector addition

Figure 2.2

Figure 2.3a