Kinematics is the branch of science which deals with the cause of the motion of any object. Kinematics is also referred to as the geometry of objects. It is an important branch of physics. It deals with the forces, motions, etc., which caused an object to move, rotate, oscillate, etc., from their place.
Average Speed vs Instantaneous Speed
The main difference between Average Speed and Instantaneous Speed is that Average speed is stated as the distance covered by the object within a period of time, whereas Instantaneous speed is the accurate speed covered by the object or a body at a given instant of time. Both the above quantities are scalar and are measured with the help of a speedometer.
Average Speed is a constant value and is measured by calculating the speed of an entire trip or journey. For a journey, it is not necessary that the body or an object remains at the average speed. Sometimes, it may have more value than the average speed or less value than the average speed depending on the path and hurdles.
Instantaneous speed is not constant for an object or a body. And it is measured with the help of the vehicle-installed speedometer. The speedometer tells the exact accurate value of the speed at that particular instant of time. The value of the instantaneous speed is greater than or equal to zero. Also, instantaneous speed is a scalar quantity.
Comparison Table Between Average Speed and Instantaneous Speed
| Parameters of Comparison | Average Speed | Instantaneous Speed |
| Definition | It is defined as the total distance traveled divided by the total elapsed time. | It is defined as the speed at a particular instant of time. |
| Formula | Total distance / Total time | The distance at that instant / Time at that instant |
| Meaning | Measured by calculating the speed for an entire journey | Measured with the help of a speedometer |
| Constant | It is constant | It is not constant |
| Example | A bike traveling with a speed of 40 miles/hour; thus, the average speed is 40 miles in an hour. | A bike traveling at a certain speed at an instant of time can be given by a speedometer. |
What is Average Speed?
It can be defined as the total distance traveled by the object or a body divided by the total elapsed time. The formula for calculating the average speed is given below –
Average Speed = Total distance traveled by the object / Total time taken by the object.
It can also be measured by calculating the speed of the entire journey or trip. It is believed that the average speed of an object or body is constant.
While traveling in a vehicle, it is quite difficult to keep the vehicle at a constant or uniform value because of the uneven structure of the road’s brakes needed to be applied, which slows down the vehicle. Thus, the speed of the body is not usually constant, and distance traveled divided by time gives us the average speed of the object or body during that time.
Consider the given an example – If a body or an object travels a distance of 100 km in 4 hours, the average speed is 25 Km/hour. It does not mean that the body is moving at the same speed throughout the journey. When the road is straight, flat, and free, the speed of the vehicle may be above the average speed, but on a curved road, hills, or in a crowded area, the speed may be slower than the average speed value.
What is Instantaneous Speed?
Instantaneous Speed can be defined as the speed of a body or an object at a particular instant in time. The formula for calculating instantaneous speed is given below –
Instantaneous Speed = The distance at an instant / Time at that instant
Instantaneous Speed can be measured with the help of a speedometer and is believed to be never constant. The instantaneous speed of an object or body is always greater than or equal to zero. It is considered a scalar quantity because it does not have a specific direction of motion.
For a uniform motion, instantaneous speed is considered a constant value. But for a particular given time, instantaneous speed is the magnitude of instantaneous velocity at that time. It is a limit of the average speed as the time interval becomes very small.
Main Differences Between Average Speed and Instantaneous Speed
- The average speed of an object or a body is stated as the total distance traveled by the object or a body divided by the total elapsed time, while the Instantaneous Speed of an object or a body can be stated as the speed of an object or a body at a particular given instant of time.
- The formula for calculating Average speed mathematically is Total distance covered by the object or body / Total time taken by the body or object, while the formula used to calculate instantaneous speed mathematically is the distance at a given time / Time at that instant.
- The average speed of the object can be measured by calculating the speed of the entire journey, whereas a speedometer helps in calculating the instantaneous speed for a given object or body.
- The average speed of an object is constant, while the Instantaneous speed of an object is not constant.
- An example of Average speed is that when a person is moving at a constant speed of 50 miles/hour, as average speed is the rate of change in the speed concerning time thus, there is no change in the speed; therefore, the average speed is 30 miles per hour while considering an example for Instantaneous speed is that the speed of the object while traveling changes concerning that instant time thus it varies and can be measured by the speedometer.
Conclusion
As kinematics deals with the cause of motion in an object or body, the two motions related to it are the average speed and instantaneous speed. The average speed for a given object is the total distance traveled divided by the total time taken. As the time interval of the trip reaches zero, the distance traveled throughout the trip also reaches zero value.
In unsophisticated words, it can be stated as instantaneous speed is considered the magnitude of instantaneous velocity at that particular given or specified time. The magnitude of the instantaneous speed can be initiate by reflecting the absolute value of instantaneous velocity. Also, the value of instantaneous velocity is always positive. The slope of the position versus time graph at a specific time gives the value of the instantaneous velocity at that time.
References
- https://ascelibrary.org/doi/abs/10.1061/(ASCE)0733-947X(2002)128:2(182)
- https://ieeexplore.ieee.org/abstract/document/148453