Speed and Velocity: Speed is a scalar quantity that refers to “how fast an object is moving.” Velocity is a vector quantity that determines “In which direction an object is moving”?

**Speed**

The speed indicates the relationship between the distance traveled by an object and the time that this used to cover it. So, therefore, it can be measured in *meters*, *kilometers*, miles, or knots (in the water environment), per hour, or per second.

Since speed is expressed according to distance and time, it is characterized by being a scalar quantity, which means that only numerical units are used to describe speed. Since speed implies covering a distance during a time interval, it can only give a positive value.

The most common way to calculate the constant velocity of an object moving in a straight line is the formula: r = d / t

*where*

r: is the rate, or speed (sometimes denoted as v, for velocity)

d: is the distance moved

t: is the time it takes to complete the movement

**Velocity**

Velocity is a *vector quantity* that refers to “the rate at which an object changes its position.” Imagine a person moving rapidly – one step forward and one step back – always returning to the original starting position. While this might result in a frenzy of activity, it would result in a zero velocity.

As the person always returns to the original position, the motion would never result in a change in position. Since velocity is defined as the rate at which the position changes, this motion results in zero velocity.

If a person in motion wishes to maximize their velocity, then that person must make every effort to maximize the amount that they are displaced from their original position. Every step must go into moving that person further from where he or she started. For certain, the person should never change directions and begin to return to the starting position.

Velocity is a vector quantity. As such, velocity is direction-aware. When evaluating the velocity of an object, one must keep track of direction. It would not be enough to say that an object has a velocity of 55 mi/hr.

One must include direction information in order to fully describe the velocity of the object. For instance, you must describe an object’s velocity as being 55 mi/hr, east. This is one of the essential *differences between* speed and velocity. Speed is a scalar quantity and does not keep track of direction; velocity is a vector quantity and is direction aware.

**How to Tell Speed and Velocity Apart**

Speed and velocity both measure an object’s rate of motion. However, speed is a scalar quantity, which means that it can be described with a numerical value. Velocity is a *vector quantity*, which depends on direction as well as magnitude. Read this definition for more information.

- speed – the rate of distance traveled by a moving object over time.
- velocity – the rate of displacement of a moving object over time

Basically, an object’s speed tells you how fast it’s going. Its velocity tells you how fast it’s going in a certain direction. You use speed measurements in your daily life, but physicists depend on velocity measurements more frequently in their work.

**Equations for Speed and Velocity**

It’s easiest to see the difference between speed and velocity when you compare their equations. In order to measure an object’s speed (s), you measure its distance (d) over time (t):

s = d/t

Once you know the object’s speed, you can calculate its average velocity by calculating the change in displacement (d) over the change in time (t):

v = Δs/Δt

This information may not seem as straightforward for an everyday traveler, but when studying physics, it’s very important to know the difference between an object’s speed and velocity.

**Notable Difference Between Speed And Velocity**

**1. **Speed is the distance covered by a body in unit time.

**2. **Velocity is the displacement covered by a body in a unit of time.

**3. **Both terms are used to refer to the relationship between the distance traveled and the time is taken to cover it.

**4. **Unlike speed, velocity accounts for both the rapidity and position of the object.

**5. **Even as, the velocity of moving Objects can be negative, positive, or can be zero. Speed cannot be negative.

**6. **Speed is the rate of change of distance while velocity is a rate of change of displacement.

**7. **Velocity determines “In which direction an object is moving”?

**8. **Both quantities are measured in m/s.

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