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Answer: The main difference between acceleration and retardation is that acceleration means an increase in velocity per second, while retardation means a decrease in velocity per second. Simply put, when an object speeds up, it is accelerating, and when it slows down, it is experiencing retardation.
Complete Answer:
Acceleration and retardation are both related to how the speed of an object changes. The table below shows how to distinguish between acceleration and retardation:
| Point of Difference | Acceleration | Retardation |
| Basic Meaning | Increase in velocity per second | Decrease in velocity per second |
| Also Called | Positive acceleration | Negative acceleration (or deceleration) |
| Velocity Change | Velocity increases over time | Velocity decreases over time |
| Nature | Positive value in formula | Negative value in formula |
| Formula | a = (v−u)/t (when v > u ) | a = (v−u)/t (when v < u ) |
| Example | A car speeding up from 20 km/h to 60 km/h | A bike slowing down from 40 km/h to 10 km/h |
| Direction of Motion | Can be in the same direction as motion | Often opposite to the direction of motion |
| Everyday Case | Falling object gaining speed | Ball thrown upward losing speed |
Acceleration refers to the increase in the velocity of an object per second. When an object speeds up, it is said to be accelerating. In simple terms, acceleration is the rate at which an object’s velocity increases over time. It is a vector quantity, which means it has both magnitude (size) and direction. For example, if a car is moving faster and faster, or if it is turning around a corner at the same speed, it is still accelerating because the direction is changing. The direction of acceleration always follows the direction of the net force acting on the object.
The formula for acceleration is:
a = (v−u)/t
Here, a is acceleration, v is the final velocity, u is the initial velocity, and t is the time taken. The unit of acceleration is metre per second squared (m/s²). If the value of aaa is positive, it means the object is accelerating. For example, if a car increases its speed from 10 m/s to 20 m/s in 5 seconds, the acceleration is:
a = (20−10)/5 = 2 m/s2
This means the car’s velocity increases by 2 m/s every second.
Retardation, on the other hand, is the decrease in the velocity of an object per second. It is also known as negative acceleration. When an object slows down, its velocity reduces, and this process is called retardation. In mathematical terms, when the final velocity is less than the initial velocity, the acceleration becomes negative. Just like acceleration, retardation also uses the same formula:
a = (v−u)/t
If the result is negative, it indicates retardation. For example, if a vehicle slows down from 20 m/s to 10 m/s in 5 seconds, the acceleration will be:
a = (10−20)/5 = −2 m/s2
This negative value shows that the vehicle is retarding, or slowing down.
Another simple example of retardation is when a ball is thrown vertically upward. Its velocity decreases as it goes up, and becomes zero at the highest point before coming back down. This decreasing velocity while going upward is a case of retardation. Just like acceleration, retardation also depends on time, velocity, and direction.
To summarize, both acceleration and retardation involve a change in velocity. If the velocity increases, it is called acceleration (positive acceleration). If the velocity decreases, it is called retardation (negative acceleration). If there is no change in velocity, then acceleration is zero. Both use the same formula, and both are measured in m/s².
Thus, acceleration helps us understand how fast something speeds up, while retardation helps us understand how quickly something slows down. These two concepts are essential in physics to describe motion accurately.
Common Physics Doubts:
