Page 24 - 11-phy-7 Oscillations

7. OSCILLATIONS eLearn.Punjab

SUMMARY

• Oscillatory motion is to and fro motion about a mean position.

• Periodic motion is the one that repeats itself after equal intervals of time.

• Restoring force opposes the change in shape or length of a body and is equal and opposite to

applied force.

• A vibratory motion in which acceleration is directly proportional to displacement from mean

position and is always directed towards the mean position is known as simple harmonic motion.
2p
• The projection of a particle moving in a circle executes SHM. Its time period T is .
w
• Phase of vibration is the quantity which indicates the state of motion of a vibrating particle

generally referred by the phase angle.

• The vibratory motion of a mass attached to an elastic spring is SHM and its time period is

T = 2p m
k

• The vibratory motion of the bob of simple pendulum is also SHM and its time period is given by

T = 2p l
g

• In an oscillating system P.E. and K.E. interchange and total energy is conserved.
• A body is said to be executing free oscillation if it vibrates with its own natural frequency without

the interference of an external force.
• When a freely oscillating system is subjected to an external periodic force, then forced vibrations

take place.
• Resonance is the specific response of a system to a periodic force acting with the natural vibrating

period of the system.
• Damping is the process whereby energy is dissipated from the oscillating system.

QUESTIONS

7.1 Name two characteristics of simple harmonic motion.
7.2 Does frequency depend on amplitude for harmonic oscillators?
7.3 Can we realize an ideal simple pendulum?

24 v: 1.1