1. The motion is the change in
position of an object with
respect to its surroundings in
a given interval of time.
Motion is always observed and
measured with a point of
reference
All living things show motion
whereas non living things
shows motion only when some
force acting on it
What is Motion?
Introduction
3. Oscillatory motion can be termed as the
repeated motion in which an object repeats the
same movement over and over. In the absence of friction,
the oscillatory motion would continue forever; but in the
real world, the system eventually settles into equilibrium.
⮚ A motion occurs even at atomic levels
can be said to be Oscillatory. When the
temperature is raised, the atoms in a
solid vibrate about their rest position
(mean position or equilibrium position).
4. ⮚ RC oscillator is used to
generate a Low Frequency
signal
⮚ LC oscillator is used to
generate a High Frequency
signal
⮚ Op-Amp based oscillator is
used to generate a stable
frequency.
For example
The study of vibrational motion is very important in
Electronics and Communication Engineering applications to
study and generate a signal.
5. What is Periodic Motion?
Motion which repeat itself after a regular interval of
time is known as Periodic motion
Periodic Motion
⮚ a bouncing ball
⮚ a vibrating tuning fork
⮚ a swing in motion
⮚ the Earth in its orbit around
the Sun, and
⮚ a water wave.
6. What is Non Periodic Motion?
Motion which does not repeat itself after a
regular interval of time is known as non-periodic
motion.
Non Periodic Motion
Example :
⮚ Occurrence of Earth quake
⮚ eruption of volcano
7. When an object or a particle moves back and forth repeatedly for
some duration of time its motion is said to be oscillatory or
vibratory. All oscillatory motions are periodic whereas all periodic
motions need not be oscillation in nature.
Oscillatory Motion
9. When the oscillator is allowed to
oscillate by displacing its position
from equilibrium position (or mean
position), it oscillates with a
frequency which is equal to the
natural frequency of the oscillator.
Such an oscillation or vibration is
known as free oscillation or free
vibration.
Free oscillations
10. In reality, in a medium, due to the presence of friction and air
drag, the amplitude of oscillation decreases as time
progresses. It implies that the oscillation is not sustained and
the energy of the SHM decreases gradually indicating the loss
of energy. The energy lost is absorbed by the surrounding
medium. This type of oscillatory motion is known as damped
oscillation.
Damped oscillations
11. By supplying energy from an external source, the
amplitude of the oscillation can be made constant. Such
vibrations are known as maintained vibrations.
Maintained oscillations
12. Any oscillator driven by an external periodic agency to
overcome the damping is known as forced oscillator or driven
oscillator. In this type of vibration, the body executing
vibration initially vibrates with its natural frequency and due to
the presence of external periodic force, the body later vibrates
with the frequency of the applied periodic force. Such
vibrations are known as forced vibrations.
Forced oscillations
13. It is a special case of forced vibrations where the frequency of
external periodic force (or driving force) matches with the
natural frequency of the vibrating body (driven). As a result the
oscillating body begins to vibrate such that its amplitude
increases at each step and ultimately it has a large amplitude.
Such a phenomenon is known as resonance and the
corresponding vibrations are known as resonance vibrations.
Resonance
14. Oscillation or Vibration – a motion that repeats
itself with no net displacement.
Equilibrium Position – the point that the object
oscillates around. Also known as the rest
position.
Displacement – how far the mass is from the
equilibrium point (x)
Maximum displacement – how far the mass moves
from the equilibrium position. (x max occurs at A)
TERMINOLOGY
15. TERMINOLOGY
Amplitude (A) – the distance from the equilibrium
point to the maximum displacement.
Cycle – a complete to and fro motion.
Period (T) – the time needed to complete one cycle.
(Unit – Seconds)
Frequency (f) – the number of cycles completed in
one second. (Unit – Hertz)
Formula
f=1/T
T=1/f
16. Any vibrating system where the restoring
force is proportional to the negative of the
displacement is called simple harmonic
motion (SHM) and is often called a simple
harmonic oscillator (SHO).
Simple Harmonic Motion
17. If an object vibrates or
oscillates back and forth
over the same path,
each cycle taking the
same amount of time,
the motion is called
periodic. The mass and
spring system is a
useful model for a SHM
system.
Oscillations of a Spring
18. We assume that the surface is frictionless.
There is a point where the spring is neither
stretched nor compressed; this is the
equilibrium position. We measure displacement
from that point (x = 0 on the previous figure).
The force exerted by the spring depends on the
displacement:
Oscillations of a Spring
19. • The minus sign on the force indicates that it
is a restoring force—it is directed to restore
the mass to its equilibrium position.
• k is the spring constant.
• The force is not constant, so the acceleration
is not constant either.
Oscillations of a Spring
21. Substituting F = kx into Newton’s
second law gives the equation of
motion:
with solutions of the form:
Simple Harmonic Motion
22. Substituting, we verify that this solution does
indeed satisfy the equation of motion, with:
The constants A and φ
will be determined by
initial conditions; A is
the amplitude, and φ
gives the phase of the
motion at t = 0.
Simple Harmonic Motion