Magnitude Of The Acceleration: 3 Facts You Should Know

As acceleration is linked to velocity change, it is a vector quantity having both magnitude and direction, just like velocity. Its direction shows how velocity is changing.  But we’re curious about what does the magnitude of the acceleration mean.

The length of any vector that points in the vector’s direction, denoted by its unit, is called magnitude. As a result, the magnitude of the acceleration is simply the acceleration vector’s length, and it is directed in the acceleration vector’s direction. This holds for any vector quantity.

⇒ Acceleration: The Vector Quantity

Physical quantities can be vector or scalar in nature. Physical quantities characterized purely by their numerical value or magnitude without considering direction are known as scalar quantities. When it comes to vector quantities, they have both.

Let’s talk about acceleration now.

Acceleration is a physical term defined as the ratio of velocity variation to time. Time, as we know, is a scalar quantity with just magnitude and no direction. Acceleration, like velocity, has two aspects: magnitude and direction. Because dividing every vector quantity by any scalar quantity yields the vector quantity. The direction of the acceleration vector will be the direction of velocity change.

But now let’s see in detail what does the magnitude of the acceleration mean?

The magnitude of Acceleration: Physical Interpretation and Mathematical Representation:-

Consider a few different ways to express the magnitude of acceleration.

❋ Magnitude of acceleration as per basic definition of acceleration:

Acceleration magnitude is nothing but the length of its vector. If we write the magnitude of acceleration, in other words, then it tells how quickly velocity varies. The unit meter per second square in the standard international (SI) system represents the magnitude of the acceleration.

If we express this sentence as an equation, it will look like this:

In this equation, vf denotes the object’s final velocity,

                          vi is its initial velocity and

                         Δt is the time interval in which the velocity varies.

Assume a car as shown in figure is traveling east and has an acceleration of 30 m/s2. The magnitude of the car’s acceleration is 30 m/s2 and the direction of acceleration is east. Now, if the car begins to progress westward at the same rate, the magnitude of the acceleration vector will remain constant, but its direction will shift towards the west.

What Does The Magnitude Of The Acceleration Mean
Car traveling with constant magnitude of acceleration

❋ The magnitude of acceleration from Newton’s second law:

In mechanics, Newton’s second law is crucial because it establishes the connection between an object’s mass and the amount of force necessary to accelerate it. A common formulation of Newton’s second law is

F = ma

, which states that the force (F) exerted on an object is equal to the mass (m) of the object times its acceleration (a). Thus we can write the magnitude of acceleration.


The above equation indicates that the greater the mass of an object, the more force is required to accelerate it. And the higher the force, the greater the acceleration of the object.

For example, thrust is the force necessary for a rocket to leave Earth’s orbit and enter outer space. To launch a rocket, Newton’s second law of motion states that the amount of thrust must be increased, which increases the acceleration. The high speed of the rocket ultimately enables it to escape Earth’s gravitational field and enter space.

❋ The magnitude of acceleration in a circular motion:

In the case of circular motion, there are two types of velocity components involved: linear and tangential. As a result, we must consider two forms of acceleration when considering the circular motion.

i) Centripetal acceleration:

Due to the numerous changes in direction, the velocity of a particle in circular motion is constantly changing. The magnitude of velocity remains constant while considering the uniform circular motion. However, because of the continuous change in direction, the particle is considered to be accelerating.

Uniform circular motion

As a result, centripetal acceleration is caused by tangential speed rather than tangential velocity. When the tangential velocity is vt, and the distance from the rotation axis is r, the magnitude of centripetal acceleration may be calculated as follows:

ac = vt2/r

ii) Tangential acceleration:

Tangential acceleration is the measure of how rapidly a tangential velocity varies with time in the circular motion of any object. Tangential velocity at the point of motion will act toward a tangent of the path. As a result, it always operates perpendicular to a rotating object’s centripetal acceleration.

Non-uniform circular motion

Multiplying the radius of a circular path and the angular acceleration of the object will give us tangential acceleration. If 𝛼 is the angular acceleration and r is the radius of the circular path, then tangential acceleration can be calculated as:

at = r𝛼

The vector sum of the centripetal and tangential accelerations yields the total acceleration vector a of circular motion.

Total acceleration in circular motion

In the case of non-uniform circular motion, the total linear acceleration vector is at an angle to the centripetal and tangential acceleration vectors, as illustrated in Figure. Since ac and at are perpendicular, the magnitude of the total linear acceleration is as follows.

⇒ Graphical Representation of magnitude of acceleration:

As we have seen, acceleration can be calculated using the following equation:

|a|= ∆v/∆t

Thus, we can calculate the acceleration from the velocity vs. time graph. The Y-axis will be represented by velocity because it is a dependent variable. And  As time is an independent variable, it will be represented by the X-axis.

Any graph’s slope is just the rise over the run or the change in the Y-axis divided by the change in the X-axis. As a result, the velocity vs. time graph slope will give us acceleration, which is the change in velocity over a given period of time.

If velocity increases with time, the graph’s slope will be positive, as seen in the graph. The object’s final velocity is larger than its initial velocity if the slope is positive.

However, the magnitude of acceleration will always be positive since the positive or negative sign reflects the direction of acceleration rather than its magnitude.

If the magnitude of the acceleration is zero, the object’s velocity will be constant throughout the motion. The slope of a graph having constant velocity will be zero, as shown in the graph below.

With this post, we aim to have answered all of your questions about the magnitude of acceleration.

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