Constant Angular Acceleration


Constant angular acceleration is an import concept of rotational dynamics. When describing a change in linear velocity, we use linear acceleration; however, when dealing with spinning bodies or objects that are moving curvilinearly, we use angular acceleration. You would not be surprised to learn that angular acceleration is the rotational counterpart of linear acceleration as the rate of rotation is the angular velocity. In contrast to angular acceleration, which defines the rate at which angular velocity changes, linear acceleration explains the rate at which linear velocity changes.

What is Angular Acceleration?

The rate at which angular velocity changes over time is known as angular acceleration. It is a three-dimensional pseudo vector. We define it in radians/second square (rad/sec2) in the S.I. unit. Additionally, we typically represent it with the Greek letter 'α’.

Interestingly, the angular acceleration is not a genuine vector nor genuinely scalar. This implies that it operates like a scalar unit because it just needs a magnitude to be completely defined, but depending on which direction you are looking, it may change the sign.

How is Angular Acceleration Determined?

We can modify the angular speed that is separated by a change in time with the aid of angular acceleration. Normal angular acceleration is easily attained with the help of this. Angle acceleration directs its motion towards the direction of the pivot. To get the degree of angular acceleration, we use an equation,

$$\mathrm{\alpha=\frac{\Delta \omega}{\Delta t}=\frac{\omega_2-\omega_1}{t_2-t_1}}$$

The frequency at which the angular velocity varies in relation to the time taken is known as the angular acceleration of a rotating object. It is the change in time that isolates the change in angular speed. The change in angular speed divided by the change in time is the normal angular acceleration.

What causes Angular Acceleration?

Acceleration is related to motion whether it is angular or linear. Thus, we know that motion is always driven by force. So, angular acceleration also has a source of the force that causes it.

We must consider the location of the force when rotating an extended object, such as a rod, disc, or cube, whose mass is dispersed over space.

Torque is a measurement of a force's capacity to initiate a spin. According to physics, the torque applied to an item relies on both the location and magnitude of the applied force. When we consider torque, which causes rotational acceleration, you move from the strictly linear concept of force as an entity that acts in a straight path.

A torque is a vector entity. The torque's magnitude provides information about its capacity to produce rotation; more precisely, the torque's magnitude is inversely related to the angular acceleration it produces. The torque is applied along the axis of the angular acceleration.

Some important terms that are associated with Angular Acceleration

Angular acceleration is a very important term when we study angular motion. There are some more terms here which are related to angular acceleration.

Angular Momentum

A rigid object's momentum is calculated by multiplying its moment of inertia by its angular rate. If there is not any external force functioning on the body, it behaves like linear momentum and it follow the fundamental rules of the conservation of momentum principle. It can be derived from the expression for a particle's momentum.



The force which will cause the associate degree object to revolve on the associate degree axis is measured as torsion. Almost like however force accelerates associate degree object in linear mechanics, torsion accelerates associate degree objects in associate degree angular direction.

Torque is additionally a vector entity. The force engaged on the axis defines the direction of the torsion vector.


Angular Velocity

The rate and direction of an object's rotation are both described by its angular velocity. The counter clockwise direction is typically seen as the positive direction. The vector representation of rotation rate, or how quickly an item rotates or revolves in relation to another point, is called angular velocity.


Some real-life applications of Angular Acceleration

Every term in Physics is very applicable in our daily life. Here we are going to study the applications of Angular momentum.

  • Grooves are carved into bullets that exit rifled barrels to give them a spinning motion when fired.

  • The football spins quickly as it goes in the air when quarterbacks toss it by adding a spin with their fingers. A tight spiral is how football fans identify a good pass.

  • Grooves that are carved into a gun's barrel provide the attractive spiral pattern that surrounds the exit hole of the muzzle.


The rotational equivalent of linear acceleration is angular acceleration. In contrast to angular acceleration, which defines the rate at which angular velocity changes, linear acceleration explains the rate at which linear velocity changes.

According to conventional wisdom, a positive angular acceleration accelerates rotation in a counter clockwise direction, whereas a negative angular acceleration accelerates rotation in a clockwise direction. The SI unit for angular acceleration is radians-per-second squared.

We split the variation in angular velocity by the change in time to determine an object's angular acceleration. This yields the angular acceleration or the mean change in angular velocity per second.


Q1. What is the significance of the positive and negative signs of angular acceleration?

Ans. The magnitude of angular acceleration is a positive number. However, we observe there are positive and negative signs with the magnitude of angular acceleration. These signs are very important in terms of the direction of the angular acceleration. When the angular speed rises counter clockwise, it is assumed that the sign of the angular acceleration is positive; when it grows clockwise, it is assumed to be negative.

Q2. How angular momentum is important for us?

Ans. In the context of angular velocity, angular acceleration is the rate at which the angle of approach changes; its magnitude and direction provide information on the rate and direction of the change, respectively.

Q3. We have a ceiling fan that starts acceleration by changing the mode from low to high. The acceleration by the blades of the Fan is 1.5 rad/s2 for 2 seconds. If the initial angular velocity was 4 rad/s. Now calculate the final angular velocity of the fan.

Ans. We know that angular acceleration is

$$\mathrm{\alpha=\frac{\Delta \omega}{\Delta t}}$$

Now, we have

Initial velocity = 4 rad/s

Angular acceleration=1.5 rad/s2

Thus, by using the equation of angular acceleration

$$\mathrm{\alpha \Delta t=\Delta \omega}$$

$$\mathrm{\alpha \Delta t=\omega_f-\omega_i}$$


$$\mathrm{\omega_f=\alpha \Delta t+\omega_i}$$



Q4. We have a newton disk that is rotating. However, it changes the speed of rotation by the rate of 50 rad/s. The change in the speed of the disk happens for 7 seconds. Now, evaluate what is the magnitude of angular acceleration for the newton disk.

Ans. By definition, we know that angular acceleration is the ratio of change in speed and time.


$$\mathrm{\alpha=\frac{\Delta \omega}{\Delta t}}$$


$$\mathrm{\alpha=7.14\: rad/s^2}$$

Updated on: 26-Apr-2023


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