Question

Define a rigid body.

Answer 1

Hint: In order to solve this you have to know what a rigid body is. What type of motion could a rigid body have? How many types of motion a rigid body have? What is translator and rotational motion? What are the examples of translatory and rotational motion?

Complete step by step answer: A rigid body is a body on which the distance between two points on the body never changes whenever an external force is being applied to it. Or we can say that a body is said to be rigid which doesn’t deform its shape under the influence of any external forces. But practically, there will be some force under which the body will change shape. For example, when a person is applying force on the bridge, it will not change shape under his weight but it might change shape under the load of five trucks, even though the deformation is very small. As in real life there is no substance which is rigid there is another concept regarding a resistant body, which is used in finding solutions for various problems of engineering. To solve a bunch of problems that could not be explained with classical physics, the rigid body and rigid body dynamics concept was developed. Motions like rotation of the fan, the potter wheel, etc. couldn’t be explained with a point mass. In a practical world, the deformation of wheel and steel rods are considered to be negligible and are considered as rigid.

Additional information: A rigid body can undergo two types of motions that are Translational motion and Rotational motion.
Translational motion: This type of motion is defined by the body moving from one point to another in space. For example: the motion of a bullet that is fired from a gun.
Rotational motion: This type of motion is experienced by the body moving in a uniform circular motion in which the body has a constant speed in a circular path and the force continuously acts perpendicular to the moving body. For example: the wheel or the rotator of a motor.

Note: Always remember that axis of rotation is the line around which a body and its every particle moves in a circular path. A stone falling straight at the surface of the earth is an example of rotational motion. Also remember that when the body has a movement along a straight line then it is known as rectilinear motion.