Definition of deceleration:

Deceleration is the decrease in velocity per unit time.

It means how quickly something is slowing down.

What is deceleration?

• Deceleration happens when an object’s velocity decreases over time.

• It is a type of acceleration but in the opposite direction to motion.

• For example, when a car presses the brakes, its speed reduces—this is deceleration.

• It doesn’t mean the object has to stop completely—just that it’s slowing down.

• In physics, we treat deceleration as negative acceleration, because the velocity is going down.

• It can happen in straight-line motion or in curved paths (like slowing down around a turn).

• The same formula for acceleration is used, but the value comes out negative when decelerating.

How deceleration helps:

• Deceleration is important for safety and control.

• It allows moving objects to slow down smoothly instead of stopping suddenly, which can prevent damage or injury.

• It’s used in vehicles, machines, sports, and even space travel.

Example:

When a car sees a red light, the driver uses the brakes to decelerate.

If the car didn’t decelerate, it would crash into the crossing.

So deceleration helps stop the car safely and in time.

Simple formula for deceleration:

Starting speed— final speed

Deceleration= ——————————————

Time taken

It’s just like acceleration, but since speed is decreasing, you subtract the final speed from the starting speed.

Example:

If a bike slows down from 20 m/s to 10 m/s in 5 seconds:

20-10

deceleration= —————- = 2m/s

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Favourite part/ note/ summary- Deceleration is the decrease in velocity per unit time. Deceleration is the opposite of acceleration. Deceleration is the decrease on velocity per unit time and acceleration is the increase in velocity per unit time. Deceleration is mainly found on vehicles like car, bike, truck etc…to slow down the vehicle. For example during a red light.