What is Retardation?

In the English language, retardation means the action of slowing down the development of a thing. But in physics, retardation means something entirely different. In simpler terms, retardation means negative acceleration. The term “acceleration” means a change in velocity. Generally, acceleration refers to an increase in velocity, but when it denotes a decrease in velocity, it is called retardation. For example, a car was running at a speed of 60 km per hour. After one hour, the velocity of the car changes to 75 km per hour. 

So, the change in velocity is 15 km per hour, so the acceleration is 15 km per hour square. Let’s assume the velocity of the car decreases to 50 km per hour. Then the change in velocity would be 10 km per hour and the value of retardation would be 10 km per hour square. As a result, when the velocity of a body increases, this is known as positive acceleration, and when the velocity of a body decreases, this is known as negative acceleration or retardation. 

Another such example is that when a train reaches a station, it slows down, and we can call it retardation. Retardation is expressed as acceleration with a negative sign. For example, if it is given that the acceleration of a body is – 45 metres per second square, then it represents the retardation of the body. The negative sign simply means that the velocity is decreasing. The SI unit for retardation is metres per second squared.