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# What is Velocity ?

The word velocity is derived from the Latin word “velocitas“. “Velocity is the rate at which an object changes its position in space.” It is a vector quantity and is expressed in m/s or km/hr. Velocity is change of position over time. In physics, velocity is a vector quantity that represents the speed and direction of an object. Velocity is the speed of an object in a given direction. Velocity has both magnitude and direction. It is the rate of change of displacement.

Major difference between speed and velocity is that, speed is a scalar quantity which has only magnitude of velocity while velocity is a vector quantity which has both magnitude and direction.

## There are several types of velocity :-

### Uniform Velocity

“Uniform velocity is the rate of change of the velocity of an object which has constant acceleration.” The velocity of an object is the rate of change of the position of an object. In uniform velocity the velocity of an object must be constant. That is why the acceleration of an object must also be constant. So, in uniform velocity the acceleration of an object must be constant. The acceleration of an object is the rate of change of velocity of an object. Uniform velocity is the rate of change of velocity which is constant. So in uniform velocity the acceleration of an object must also be constant.

### Average Velocity

“The average velocity is the distance travelled over a given time period divided by the time period.”
The average velocity of a body is equivalent to the average speed. Average velocity may change when the body changes the direction or the initial velocity changes. The average velocity is always positive. Average velocity is used for a single particle and for a system of particles. Average velocity is used to calculate the average velocity of a body if the average acceleration is known.

Average velocity = (total distance)/(total time)

### Instantaneous Velocity

“The instantaneous velocity is the rate of change of an objects displacement with respect to time.” The magnitude of the instantaneous velocity is the instantaneous speed. It is a vector quantity which has both magnitude and direction. Instantaneous velocity is usually denoted by a small letter “v”. The SI unit of instantaneous velocity is m/sec. It can also be calculated by taking slope of distance time graph. instantaneous velocity is calculated for an object under motion at an specific point of time.

Instantaneous velocity = (final position – initial position)/time elapsed

### Non-Uniform Velocity

“The non-uniform velocity is the rate of change of velocity of a body at a particular instant of time.” It is the velocity at the end point of a given time interval. The non-uniform velocity is not a constant value. It is generally a function of time. The non-uniform velocity of a body depends on the magnitude and direction of the velocity as well as the velocity at the starting point. It is a vector quantity. It is a function of time and the magnitude of the velocity. It is the derivative of the velocity with respect to time. It is a measure of the rate of change of velocity with respect to time. The non-uniform velocity is the velocity at any instant of time.”