Chapter 8
Motion
Introduction
• One of the most common phenomena in the physical world is motion. Mechanics is the branch of Physics that deals with the behaviour of moving objects.
• Mechanics is divided further into two sections: Kinematics and Dynamics.
• Kinematics is the study of motion without regard for the cause of motion.
• Dynamics is concerned with the source of motion, which is force.
Motion and Rest:
• An object is said to be in motion if its position in relation to its surroundings changes in a given time.
• An object is said to be at rest if its position in relation to its surroundings does not change.
• A frame of reference is another object or scene against which we compare the position of an object.
Types of Motion:
There are three types of motion:
• Translatory motion
• Rotatory motion
• Vibratory motion
Translatory Motion:
• A particle in translatory motion moves from one point in space to another. This movement may be in a straight line or in a curved path.
• Rectilinear motion is defined as motion along a straight line.
• Curvilinear motion is defined as movement along a curved path.
• As an example, consider a car driving down a straight road.
Rotatory Motion:
The particles of the body describe concentric circles around the axis of motion in rotatory motion.
Vibrational Motion:
Particles in vibratory motion move back and forth around a fixed point.