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MUST

KNOW Important Definition

Damping and Resonance Physical Quantities
• Free vibrations are the vibrations of a system at its natural
frequency without external disturbance. Terminology Explanation
Physical quantity Must be measurable
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• Damped vibrations are the vibrations of a system where the
amplitude decreases with time due to resistive forces. Cannot be defined in terms of other
Base quantity
quantities
• Forced vibrations are the vibrations of a system caused by
external alternating forces. Derived from combinations of base
Derived quantity quantities through multiplication or
division or both
• When a periodic force is applied to an oscillating system at
its natural frequency, the oscillating system is said to be at Scalar quantity Has magnitude only
resonance.
Vector quantity Has both magnitude and direction

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Fundamentals of Waves and Oscillations Experimental Design
• Oscillation and vibration are repetitive motions about an
equilibrium position in a closed path. Manipulated Variable The variable you will change before
(MV) carrying out the experiment.

• Amplitude is the maximum displacement of an oscillating Responding Variable The variable you will measure in
object from its equilibrium position. (RV) responding to the change in the MV.
Constant Variable Any other variables which could
• Frequency is the number of complete vibrations per second. (CV) affect the outcome of the experiment
Unit of frequency is hertz (Hz). but you set to remain constant
throughout the experiment.
• Period is the time taken for one complete oscillation.
Example: The simple pendulum experiment
MV: Length of pendulum, l = 20.0 cm, 30.0 cm…
• Waves are produced when a system oscillates or vibrates in 70.0 cm
a medium or field. RV: Time taken for 20 complete oscillations
CV: Mass of pendulum bob
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Total Internal Reflection and Critical Angle Inertia
• When a ray of light propagates from a denser medium to a • Inertia of an object refers to the reluctance of the object to
less dense medium, total internal reflection is said to occur change its state of rest or motion due to its mass.
when the angle is incidence is greater than the critical angle.
• Inertia is non-physical quantity. It is an attribute only.
• The critical angle, c, is the angle of incidence of light,
moving from a denser medium towards a less dense medium
where the angle of refraction is equal to 90°.
n = 1
sin c

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Must Know QBank Physics F4.indd 2 14/01/2022 5:08 PM