Inaugurated by IN-SPACe
ISRO Registered Space Tutor
S6-SA3-0384
What is Free Vibrations?
Grade Level:
Class 10
AI/ML, Physics, Biotechnology, Space Technology, Chemistry, Engineering, Medicine
Definition
What is it?
Free vibrations happen when an object vibrates on its own after being disturbed just once and then left alone. It moves back and forth at its natural frequency without any continuous external force pushing it.
Simple Example
Quick Example
Imagine a child on a swing. You give the swing one big push and then let go. The swing will keep moving back and forth for some time, slowly slowing down, until it stops. This back-and-forth motion after the initial push is a free vibration.
Worked Example
Step-by-Step
Let's say you have a simple pendulum, like a small stone tied to a string.
1. Hold the string and let the stone hang still.
2. Gently pull the stone to one side (disturb it).
3. Release the stone. Do NOT push it again.
4. Observe the stone swinging back and forth.
5. Notice that it swings with a regular rhythm (its natural frequency) but slowly loses height and eventually stops.
This entire motion, from release until it stops, is free vibration.
Why It Matters
Understanding free vibrations is crucial in engineering to design structures like bridges and buildings that don't collapse due to resonance. In space technology, it helps predict how satellites will move after a small nudge. Mechanical engineers use it to ensure machines run smoothly and safely.
Common Mistakes
MISTAKE: Thinking free vibrations need continuous pushing. | CORRECTION: Free vibrations occur after an initial disturbance, without any further external force.
MISTAKE: Confusing free vibration with forced vibration. | CORRECTION: Free vibration is when an object vibrates at its natural frequency; forced vibration is when an external force continuously pushes it at a different frequency.
MISTAKE: Believing free vibrations continue forever at the same amplitude. | CORRECTION: Free vibrations slowly decrease in amplitude due to damping (like air resistance) and eventually stop.
Practice Questions
Try It Yourself
QUESTION: A guitar string is plucked once. What type of vibration does it exhibit? | ANSWER: Free vibration
QUESTION: A car's suspension system is designed to absorb shocks. When the car hits a speed breaker and then settles down, the up-and-down movement of the car after hitting the breaker is an example of what? | ANSWER: Free vibration
QUESTION: A tuning fork is struck on a rubber pad and then held in the air. It vibrates and produces sound. If no one touches it again, will its vibration continue forever with the same intensity? Explain why. | ANSWER: No, its vibration will slowly decrease in intensity and stop. This is because of damping forces like air resistance and the energy being converted into sound.
MCQ
Quick Quiz
Which of the following is an example of free vibration?
A car engine running continuously
A child being continuously pushed on a swing
A pendulum swinging after an initial displacement and then left alone
A mobile phone vibrating due to an incoming call
The Correct Answer Is:
C
Option C describes an object disturbed once and then left to vibrate on its own, which is the definition of free vibration. Options A, B, and D involve continuous external forces or energy input.
Real World Connection
In the Real World
When a metro train passes near a building in Delhi, the building might shake slightly for a few seconds and then settle. This initial shaking and settling, without the train continuously pushing the building, is a form of free vibration. Civil engineers study this to ensure buildings are stable and safe.
Key Vocabulary
Key Terms
NATURAL FREQUENCY: The specific frequency at which an object naturally vibrates when disturbed. | AMPLITUDE: The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. | DAMPING: The gradual reduction in the amplitude of an oscillation due to energy loss. | EQUILIBRIUM POSITION: The position where a vibrating object rests when not in motion.
What's Next
What to Learn Next
Great job understanding free vibrations! Next, you should explore 'Forced Vibrations and Resonance'. This concept builds on what you've learned by showing what happens when an external force continuously acts on a vibrating object, leading to interesting and sometimes powerful effects.
