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.
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