15 April 2020

Difference between speed and velocity | Speed vs velocity

As we know, speed and velocity are the two most common key terms in the field of physical science and engineering. Most of the times these terms confuse the newbie or those who just started learning the physics sciences and engineering.

Definition of speed:

The distance covered by a body in a given interval of time is called speed.  It is a scalar quantity as we need only its magnitude, but not the direction to specify it. It can be understood as the rate at which a body travels a distance, in the unit time. It determines the quickness of the object. i.e how fast an object is going. The meter per second is the SI unit of speed. The most commonly used unit of speed in kilometers per hour.

Definition of velocity:

The displacement of something in a definite time is called velocity. It is a vector measurement, as contains both the components i.e magnitude and direction. Therefore while the velocity of the object one must keep in mind that the direction should be special mentions, with a view to explain velocity completely.

The main key difference between speed and velocity are listed below:

  • Speed is the rate at which an object covers a certain distance while the velocity can be defined as the rate at which an object changes position in a certain direction. 
  • Speed is a scalar quantity while the velocity is the vector quantity.
  • The average speed will continue to count even if the object if direction while the velocity of the object is direction, therefore the object must follow one direction.
  • Speed is non-directional, while the velocity has direction.
  • Speed can never be negative or zero, velocity magnitude can be zero, negative or positive.
  • Speed may or may not be equal to the velocity, While in velocity An object may possess different velocities but the same speed. 
  • Both speed and velocity SI unit of m/s.
  • Speed never decreases with time. For moving objects. It is never zero. But the velocity can decrease with time. For a moving object. It can be 0.
  • V = d/t where the v is the average speed, t is the time taken to travel the distance and d is the distance traveled while the velocity is V = Δx/Δt, where is the average velocity Δt is the time of arrival and Δx is the displacement.
  • Speed determines how fast something is moving? while the velocity determines what direction something is moving?
  • A sports bike traveling at 50 m/s would go from 0 m/s to 30 m/s. before reaching 50 m/s and could even reach around 70 m/s. However, the average speed will be the speed of the bike while in velocity example is that a train going towards the south with an average speed of 50 km/h will have a velocity of 50 km/h, north. An object going straight in a particular direction is considered to have a velocity. 
Similarities between speed and velocity:
  • Measures how fast an object is traveling.
  • SI unit meter/second