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Vibration is the oscillatory motion of a body about its equilibrium position. When a system is displaced from its rest position and allowed to move, it tends to swing back and forth due to internal restoring forces. This repeated motion is called vibration.
Vibrations are present everywhere in engineering systems—machines, vehicles, structures, engines, turbines, bridges, and even in the human body.
What Causes Vibrations?
Vibrations occur when three basic elements interact:
Mass – provides inertia
Stiffness – provides restoring force
Damping – dissipates energy
When a mass attached to a spring is disturbed, the spring tries to bring it back to equilibrium, and the mass overshoots due to inertia, creating oscillatory motion.
Examples of Vibrations in Daily Life
A plucked guitar string vibrating
Vehicle suspension moving on a rough road
Fans and motors vibrating during operation
Buildings vibrating during earthquakes
Washing machine shaking during spin cycle
Types of Vibrations (Basic Idea)
Free vibration – occurs after an initial disturbance without continuous force
Forced vibration – caused by continuous external force
Damped vibration – amplitude decreases with time due to resistance
Undamped vibration – ideal case with no energy loss
Important Terms
Cycle: One complete oscillation
Time period (T): Time for one cycle
Frequency (f): Number of cycles per second (Hz)
Amplitude: Maximum displacement from mean position
Natural frequency: Frequency at which a system vibrates freely
Why Study Vibrations?
Understanding vibrations is crucial because excessive vibration can:
Cause noise and discomfort
Lead to fatigue failure of components
Reduce machine life
Cause structural damage
At the same time, controlled vibrations are useful in:
Sieving and screening machines
Compaction equipment
Musical instruments