Velocity is an essential concept in physics, which measures the rate of change of an object’s position with respect to time. When the speed of an object is measured in a specific direction, then it is termed Velocity. Also, the time-rate change of displacement is known as velocity. Both speed and velocity are quite similar to each other. But exhibits an important difference in that velocity is a vector quantity that has both magnitude and direction. And speed is a scalar quantity that has magnitude only. Thus, Velocity is a measure of how much time a body takes to reach a destination with direction.

For example, when two objects are traveling in the same direction, then it is easier to tell the faster. But, if the direction of motion of the two objects is in the opposite direction, then it is difficult to identify the fastest. In such situations, the concept of velocity is essential.

Velocity Definition

Velocity is defined as  the rate of change of the position of the object with respect to a frame of reference and time

 

Velocity is a vector measure of the speed and direction of movement. Simply put, velocity is the pace at which something moves in a particular direction. The speed of a car going north on a major highway and the speed of a rocket bursting into space may both be measured using speed. As one may anticipate, the scalar size (total value) of vector velocity represents the speed of movement. In terms of computations, speed is the first exit of a place in terms of time. Speed can be calculated using a simple formula using measurement, distance, and time.

Unit of Velocity

• The SI unit for velocity is m/s (meters per second).
• At the same time, velocity can be expressed in any unit of distance. Other units include miles per hour (mph), kilometers per hour (kph), and kilometers per second (km/s). 

Types of Velocity

There can be various types of velocities for any object, some of these types are as follows:

• Uniform Velocity 
• Non-Uniform Velocity
• Instantaneous Velocity
• Average Velocity

Let’s understand these velocities as follows:

Uniform Velocity 

When any object travels equal displacements in equal times then its velocity is called uniform velocity. A train traveling at a constant speed of 80 kilometers per hour (km/h) for 2 hours will cover a distance of 160 kilometers (km), then the velocity of a train traveling at 80 kilometers per hour is an example of Uniform Velocity.

Non-Uniform Velocity

When any object travels unequal displacements in equal time intervals then its velocity is called non-uniform velocity. For example, a car traveling at 30 km/h in a crowded street, then accelerating to 80 km/h on a highway, and then slowing down to 50 km/h in a suburban area, then the car is said to be having non-uniform velocity.

Instantaneous Velocity

Velocity at a certain moment or over a very short period of time for any object is called instantaneous velocity. Let’s consider a car traveling at a constant speed of 100 km/h on a highway, and the driver looking at the speedometer to see its velocity is an example of instantaneous velocity at that moment.

Average Velocity

For a moving object with some velocity, the total distance traveled per unit of time is called the average velocity of that object. i.e.,

Average Velocity = Total Displacement Travelled / Total Time Taken

Let’s consider, a person walks a distance of 4 km in 1 hour, then walks another 2 km in 30 minutes. The average velocity for the whole trip is 8 kilometers per hour (km/h).

Initial and Final Velocity

Initial Velocity is the velocity when the motion of the object started. In simple words, the velocity at a time interval t = 0 s is called the Initial velocity. It is represented by the symbol u. The SI unit is similar to that of the velocity i.e. m/s.

Final Velocity is the velocity attained by the object when it reaches maximum acceleration. In simple words, the velocity gained by the object at a certain time interval is called the Final velocity. It is represented by the symbol v. The SI unit of both initial and final velocities are the same i.e. m/s.

How to find the final velocity?

Follow the following steps to find the Final velocity of the object.

Step 1: The object’s initial velocity can be calculated by dividing the total distance traveled by the amount of time it took the object to travel that distance. In the formula V = d/t, V is the speed, d is the distance, and t is the time.

Step 2: By dividing the mass of the object by its force, then multiplying the result by the acceleration’s time, you can determine its acceleration.

Step 3: To get the final velocity, add the amounts from Steps 1 and 2.

Constant Velocity

The constant velocity of an object is gained when it has a constant speed in a constant direction. Here the constant direction restricts the object to move in a linear or straight path. Therefore, the constant velocity is then termed as the motion of the object in a straight line at a constant speed.

One of the simplest forms of motion is when the object moves with a constant velocity. Such a constant motion can be witnessed whenever an object slides over a horizontal surface.

However, a bicycle moving at a constant of 50 km/h in a circular path has a constant speed but does not have a constant velocity because its direction changes following the circular path.

Velocity Formula

There are different formulas to calculate the velocity of an object using different parameters under various conditions. Here are some of the major formulas used to calculate different velocities as-

When the initial (x_i) and the final position (x_f) of an object along with the time interval are given, then the velocity can be calculated as,

 

Now, according to the Equations of motion, the velocity can be evaluated,

• When initial velocity, acceleration, and time are given then the final velocity is given as,

 

where

• v is the final velocity, 
• u is the initial velocity, 
• a is the acceleration and 
• t is the time taken by the object.

Difference between Speed and Velocity

Speed and velocity are terms that are often used in a similar manner so are a little confusing for most of us. But, practically there is a significant difference between both of the terms. 

The term Speed is used to express how fast a body is moving. However, velocity not only expresses its speed but also briefs us about the direction in which the body is moving.

Hence, speed is simply defined as the rate of change of the distance traveled by an object in a given time interval. While velocity is defined as the rate of the displacement of an object in a given time interval. This implies that speed is the function of distance and velocity is the function of displacement. And most importantly, speed is said to have magnitude only so is a Scalar quantity, while velocity has both magnitude and direction, it is a vector quantity. Moreover, both quantities have the same units and dimension formulas. 

The difference between Speed and Velocity in tabular form is given as follows: