In Physics, Speed and Velocity are both fundamental concepts that describe the rate of change of position of an object. Conceptually, they are quite similar, but some differences make each term significant and useful in physics.
Speed is a scalar quantity that refers to the distance covered by an object per unit time. It measures the magnitude of the object’s motion, regardless of direction. As indicated in the definition the two quantities involved in the formula are distance and time. Whenever “per unit time” is mentioned, it means a quantity is being divided by time, which here would be distance/time. When the values of total distance and time are used in the formula, the distance covered by the object per unit second (s) will be obtained which is speed. So the formula for speed is Speed = Distance/Time. Speed is always positive or zero and is measured in units such as meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph). However, the SI unit is m/s.
Figure 1.1
For example, imagine the car in the above figure travels to the beach which is at a distance of 100 kilometers in 2 hours. The speed of the car would be calculated by dividing the total distance traveled by the total time taken. In this case, the speed would be 50 kilometers per hour (km/h) which in SI units will be 50/3.6 = 13.89 m/s.
Figure 1.2
Whereas, Velocity is a vector quantity that is the same as speed but also with the direction of the object’s motion. Since it considered direction, instead of using distance, the formula uses displacement which is distance + direction. Velocity can be positive, negative, or zero, depending on the direction of the motion. It is measured in units such as meters per second (m/s), kilometers per hour (km/h), or miles per hour (mph), along with the specified direction which can be as simple as north, east, south, and west.
Figure 1.3
Using figure 1.1 again, imagine the car travels to the beach which is in the east in 2 hours and then returns back to the starting point in another 2 hours. The car's velocity would be calculated by dividing the total displacement (change in position) by the total time taken. In this case, since the car returns to the starting point, the displacement would be zero, hence the velocity would also be zero: 0/4 = 0. If we were to find the speed here, we would divide the total distance by the total time taken: (100 x 2)/(2+2) = 200/4 = 50 km/hr.
In the case above, if the car travelled beyond the starting point while returning then the velocity would be negative as the displacement would be negative.
Understanding the distinction between speed and velocity is important in physics, as it allows us to accurately describe and analyze the motion of objects. Head over to the articles section to learn more interesting concepts.
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