Unit IV- Vectors and Three-Dimensional Geometry

There are two types of physical quantities vector quantity and scalar quantity

Scalar quantity

The quantities which are the only magnitude are called scalar quantities for example time

Vector quantity

The physical quantities which have both direction and magnitude are called vector quantities for example velocity

How can we find the magnitude of a vector

Let A = 2i+3j+4k 

Magnitude of vector = ✓2²+3²+4²

                                    = ✓ 4+9+16 = ✓ 29 

Three dimensional Geometry

i ,j and k 3 unit vectors in direction of x axis y axis and z axis

Direction cosine give the angle with which align makes an angle with the axis formula for the direction cosine is

l = a cos ¢

m = b cos ¢ 

n = c cos ¢ 

Where a b and c are the direction ratios