Unit of Acceleration: SI Unit, Types, Formula and Real-Life Examples

The unit of acceleration is the most crucial topic in the subject of physics. Though it is a factor that we cannot perceive with our senses, it has an impact on all objects which move such as bicycles, automobiles, planets, satellites, etc. Now comes the crux of the matter. Acceleration is not only a number. Apart from providing information on the rate of speed change, it also indicates the direction in which the speed changes. With advancement in science, there are numerous applications of acceleration in various fields like engineering, transportation, astronomy, etc. This article gives an insight into the topic of the unit of acceleration, measuring systems, and real-life examples.

Table of Contents

• What is acceleration
• Unit of Acceleration
• Other Units of Acceleration

What is Acceleration

Acceleration isn’t just a number; it’s a way to understand how something’s motion is changing. It tells us how quickly an object speeds up or slows down and whether its direction is shifting. Think about driving a car. If you start at 30 km/h and gradually speed up to 60 km/h to keep up with traffic, your car is accelerating. But acceleration doesn’t only mean going faster; if the car slows down or takes a turn, it’s accelerating in that direction too. So, in simple words, we can say that,

• When the speed goes up, it’s called positive acceleration.
• When the speed goes down, it’s negative acceleration, also known as deceleration.

In other words, we can say that acceleration is all about change, whether in speed, direction, or both, and it helps us understand how objects move in real life.

Unit of Acceleration

Acceleration is all about how quickly the velocity of an object changes over time. To measure this, we have different units depending on the system of measurement. Let’s take a closer look.

1. SI Unit of Acceleration

In the Système International (SI) system,

• Velocity is measured in meters per second (m/s)
• Time is measured in seconds (s)

The SI unit of acceleration is meter per second squared (m/s²). This means that if an object’s velocity changes by 1 meter per second in 1 second, its acceleration is 1 m/s². Mathematically, it is expressed as,

a=ΔvΔt

Where:

• Δv = change in velocity (m/s)
• Δt = change in time (s)

So, whenever you see an object speeding up or slowing down in metres per second each second, that’s its acceleration in SI units.

2. C.G.S. Unit of Acceleration

The Centimetre-Gram-Second (C.G.S.) system works slightly differently:

• Length is measured in centimetres (cm)
• Time is measured in seconds (s)

Here, acceleration is expressed as cm/s². It tells us how many centimetres per second the velocity of an object changes every second.

3. Foot per Second Squared (ft/s²)

The Foot-Pound-Second (FPS) system uses feet per second squared (ft/s²). This is similar to the SI and C.G.S. systems but uses feet instead of metres or centimetres. For example, if a body’s speed changes by 1 foot per second in 1 second, the acceleration is 1 ft/s².

Other Units of Acceleration

Acceleration doesn’t always have to be measured in metres per second squared. Depending on the system you’re using or the context, there are several different units. Let’s take a closer look at all of them.

1. Gal Unit of Acceleration

The Gal is named after Galileo Galilei, the scientist who studied gravity. This unit is mainly used for measuring gravitational effects.

• 1 Gal = 1 cm/s²
• In SI units: 1 Gal = 0.01 m/s²

Think of it as a way to see how gravity or other forces make an object speed up or slow down.

2. Standard Gravity (g or g-force)

When we talk about gravity on Earth, we often use 'g' or 'g-force'.

• Standard gravity is roughly 9.8 m/s²
• It’s called g-force in many situations, like when pilots fly fast, or you ride a roller coaster.

Even though it’s called g-force, remember it’s about acceleration, not the force itself. It tells us how fast something speeds up due to gravity.

3. Planck Acceleration (ap)

Named after Max Planck, this unit describes incredibly high acceleration, basically, speed changes that go all the way up to the speed of light.

• Mostly used in theoretical physics and cosmology
• Helps scientists think about extreme conditions in the universe

4. Acceleration due to Gravity (g)

This is often confused with standard gravity but is slightly different.

• Represented by ‘italic g.’
• Refers to the natural acceleration experienced by a free-falling object near Earth
• Value near the Earth’s surface: 9.8 m/s²

So, when something falls, this is the acceleration acting on it because of Earth’s pull.

5. Angular Acceleration (α)

When objects spin or rotate, they can speed up or slow down in their rotation. That change is measured by angular acceleration.

α=ΔωΔt

Where:

• Δω = change in angular velocity (rad/s)
• Δt = time (s)
• SI unit: rad/s²

It’s just like linear acceleration, but for spinning motion.

6. Centripetal Acceleration

If something moves in a circle, it constantly changes direction. That change in motion toward the centre of the circle is centripetal acceleration.

• SI unit: m/s²
• Every time you go around a bend in a car or ride a Ferris wheel, this acceleration is at work.

7. Radial Acceleration

Radial acceleration is very similar to centripetal acceleration. It’s the acceleration along the radius of a circle, pointing straight to the centre.

ar=v2r

Where,

• v = angular or tangential velocity (rad/s)
• r = radius of the circular path (m)
• SI unit: rad/s², same as angular acceleration

To make it simpler, here’s a quick table summarising all the units of acceleration, their symbols, and what they represent:

Unit Type	Symbol	Value
SI unit	m/s²	Standard metric unit
C.G.S. unit	cm/s²	Centimeter-Gram-Second system
Foot per second squared	ft/s²	FPS system
Gal	Gal	1 Gal = 1 cm/s² = 0.01 m/s²
Standard Gravity	g	~9.8 m/s²
Planck Acceleration	ap	Extreme acceleration near the speed of light
Angular Acceleration	α	rad/s²
Centripetal Acceleration	–	m/s²
Radial Acceleration	ar	rad/s

Now that we’ve gone through all the different types of acceleration and how they are measured, it’s easier to see the big picture. 

In this article, we discussed that each unit has its own context, whether it’s spinning objects, free-falling bodies, or theoretical extremes, but they all describe the same basic idea: how quickly something changes its velocity.