Study Notes on Motion

Motion :A body is said to be in motion if it changes its position with respect to its surroundings as time goes on. A body is said to be at rest if it does not change its

position with time, with respect to its surroundings.

TYPES OF MOTION

(i) When a particle or a body moves along a straight path, its motion is Rectilinear or translatory motion.

(ii) When a particle or a body moves in a circular path, its motion is circular motion. When a body spins about its own axis, it is said to be in rotational motion.

(iii) When a body moves to and fro or back and forth repeatedly about a fixed point in a definite interval of time, it is said to be in vibrational or oscillatory motion

SPEED

The time rate of change of position of an object in any direction i.e. the rate of change of distance of an object with respect to time is known as speed.

VELOCITY

The rate of change of displacement of an object with respect to time is known as velocity.

ACCELERATION

The rate of change of velocity with respect to time is called acceleration. When a body completes equal displacement in equal interval of time, its velocity is constant and hence, it does not have an acceleration. When a body shows equal change in velocity in equal interval of time its velocity is not constant but it has a constant acceleration

EQUATIONS OF MOTION

POSITION (DISPLACEMENT)-TIME GRAPHS

(i) For a body moving with a uniform velocity: 

This graph comes as a straight line because in a uniform velocity the particle completes equal displacement in an equal interval of time.

(ii) For the motion of a body thrown vertically upwards : 

When the body moves up, its velocity continuously decreases due to gravity and finally becomes zero at the maximum height. Then, the body falls with an increasing velocity.The slope of the position time graph is equal to the uniform velocity.