Physicists use the basic quantities of speed and velocity to describe the motion of objects in terms of distance, time, and direction. There are two distinct meanings for these two terms. Nonetheless, we frequently hear these terms used interchangeably. So, what’s the distinction? Why is it incorrect to use the terms velocity and speed interchangeably? In this article, you will learn the difference between speed and velocity.
What is speed?
The distance traveled per unit time is defined as speed. In the same amount of time, a man traveling by car will cover a greater distance than a man traveling by bicycle. This is due to the fact that a car can travel at a faster speed than a bicycle. In kinematics, speed is the magnitude part of velocity, so it is a scalar quantity. The formula of speed is given as follows:
speed = distance / time
Its SI unit of speed is meter per second (m / s).
Several terms related to speed, also known as types of speed, are discussed below:
Instantaneous Speed: The speed at any given time is referred to as instantaneous speed. For example, any vehicle’s speedometer can display instantaneous speed. It is defined as the magnitude of the instantaneous velocity, which is the derivative of the position with respect to time.
V = dr / dt
Average Speed: Unlike instantaneous speed, average speed is the total distance traveled in a given time interval. In other words, the average speed of the body is the total distance traveled divided by the total time interval.
Rotational Speed: The rotational speed of a body is the number of turns it makes in one unit of time.
Tangential Speed: The linear speed of a body traveling along a circular path.
Tangential Speed= rotational speed x radial distance
V = r ω
Thus, tangential speed is directly proportional to r when all parts of a system have the same, as in the case of a wheel, disk, or rigid wand.
Relative Speed: As the name implies, the speed of any body is relative to any other body, and the speed of one body can be seen in relation to another.
Uniform Speed: A body’s speed is uniform when the distance it travels in equal intervals of time.
Non-uniform Speed: When a body’s distance traveled in an equal interval of time is unequal, the speed is said to be non-uniform.
What is velocity?
Velocity is defined as a physical vector quantity. It has both a magnitude and a direction. The velocity in calculus is the first derivative of the position with respect to time. In other words, velocity is the rate of change in the position of the body with respect to time. It SI unit of velocity is meter per second.
Velocity = displacement / time
Relative Velocity: A measurement of velocity between two objects determined in a single coordinate system is referred to as relative velocity.
Similar to speed, there are several types of velocity, which are denoted as:
Terminal velocity: A constant velocity attained by a freely falling object when the resistance of the medium through which it is falling prevents further acceleration.
The instantaneous velocity of an object is the limit of the average velocity as time approaches zero, or the derivative of x with respect to t:
dx / dt = v(t)
Like average velocity, instantaneous velocity is a vector with a dimension of length per time.
Difference between speed and velocity
Although both speed and velocity are measured in m/s, but there are many differences between speed and velocity. The difference between speed and velocity is straightforward and easy to understand.
Speed is the rate at which an object moves along a path in time, whereas velocity is the rate and direction of movement.
- Velocity is a vector, whereas speed is a scalar value.
- Velocity is defined as the rate of change of position of an object whereas speed is the rate at which an object covers certain distance.
- The mathematical calculation for speed is relatively simple. You just need to divide the distance traveled by the time it took to travel the distance, to calculate the average speed of an object. Velocity, on the other hand, is more mathematically complex and can be calculated in a variety of ways depending on the information available about the object’s motion. Average velocity is calculated in its most basic form by dividing the change in position (r) by the change in time (t).
- Speed is the distance covered in unit time whereas velocity is the displacement covered in unit time.
- Velocity can be negative but speed can never be negative.
- Speed only determines the magnitude that is how fast is a body moving whereas velocity determines the direction also that is in which direction the body is moving.
- An object can possess the same speed and different velocities. Speed may or may not be equal to the velocity.