Question

Define the terms rotational motion and rotational dynamics.

Answer 1

Hint:Rotational motion, as we can understand from the name itself, is defined as the motion of a point in a circular path, where the center point is fixed on the fixed axis of rotation. If the rotational motion is considered without considering its causes, it is known as rotational kinetics and if the causes of the rotational motion are considered along with its properties, it is known as rotational dynamics.

Complete answer:
Let us understand the concept of rotational motion first. If all the particles of a rigid body perform circular motion and the centres of these circles are steady on a definite straight line called axis of rotation, then the motion of the rigid body is called the rotational motion.In simple words, we can say that rotational motion is defined as the motion of an object in a circular path around a fixed point.

As we have considered a rigid body, we can understand that the angular velocity of every particle will also be equal.Now, if we consider the rotational motion without considering the cause of the rotational motion and the change in its properties, it is known as rotational kinematics.However, if the causes of the rotational motion are considered along with the constant and changing properties of the body, we define it as rotational dynamics.Rotational dynamics involves the brief study of the system and the study of the parameters of the body when it is in motion.

We can study the rotational dynamics by defining certain parameters like angular displacement, angular velocity, and angular acceleration. We also need to define certain intrinsic properties like Moment of inertia, centre of mass etc.As we are studying the forces and motion of the body, Newton’s Laws of motion will be applicable here by changing the linear coordinates to angular coordinates. Similarly we can apply the equations for uniformly accelerated motion.

Note:Here, we should have a clear idea about the difference between the circular motion and the rotational motion. The basic definition which includes the motion of the body around a fixed point known as axis of rotation is same for both, the only difference is that for rotational motion the fixed point or axis of rotation lies within the body, whereas for circular motion the axis of rotation is located at a certain distance outside the body.