Distance

Distance is the measure of the total movement of the object between two points without considering the direction of motion of the object. If a person is walking 20 metres in the north direction and then 20 metres in the east direction. The total distance travelled will be the sum of the two numbers. The total distance is equal to 40 metres. The SI unit of distance is metres.

The distance between two points cannot be a negative quantity. In other words, distance never decreases. The distance can be zero only when the object is at rest, for a moving object distance cannot be zero.  Distance is a scalar quantity. Scalar quantity only has magnitude and not direction. What is the formula for distance? The formula for distance can be written in terms of speed

Distance = speed x time

d = s x t

d is the distance between the two points

s is the speed

t is the time

Displacement

Displacement is the shortest distance between two points. It is a vector quantity that depends on the magnitude and direction. For example, the man travelling 20 km south is the displacement. The displacement value can be positive or negative or zero. The SI unit of displacement is metres.

Speed

The speed of the object is the distance travelled by the object in unit time.

Speed = distance/ time

The speed of the object depends on the scalar quantities like distance travelled and time. Therefore, speed is also a scalar quantity. The speed of the object cannot be negative or zero. The speed will only be a positive value. The unit of speed is m/s.

Velocity

The velocity of the object depends on the displacement. Velocity is given by the ratio of displacement by time.

Velocity = displacement/time

The displacement of the object is a vector quantity. Therefore, velocity is also a vector quantity. The velocity can be positive, negative or zero. The SI unit of velocity is m/s.

What is the Difference Between Speed and Velocity?

When the motion of the object is described in terms of distance, displacement and time we use the quantities speed and velocity. Speed and velocity have two distinct meanings. But it is very common to hear these words used interchangeably. So, What is the difference between speed and velocity? What are the reasons we should not interchange these terms? The speed is the measure of the time rate of movement of the object along a path while velocity is measured in terms of the time rate and direction of the object’s motion.

The speed of the object is dependent on the distance travelled by the object while velocity depends on the displacement of the object. Speed is a scalar quantity and velocity is a vector quantity. Speed is always positive while velocity can be negative, positive or zero. Speed is much simpler to calculate while velocity is a complicated mathematical calculation.