Vibratry motion

It is useful for students

1. VIBRATORY MOTION And wave PREPARED BY: M USAMA ZAHID (045) HASSAN Raza (73) M Inam (76) M Ikram (23)

2. Definition of vibratory motion Vibratory motion occurs at a fixed point as an object moves back and forth. Any motion that repeat itself after an interval of time is called Vibratory Motion.

3. Examples of Vibratory motion

4. Properties Of Vibrating object Frequency Amplitude Time period

5. Amplitude Amplitude , the maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path.

6. Frequency Frequency, number of cycle that pass a fixed point in unit time. Unit of frequency is hertz (Hz)

7. Time period A period T is the time needed for one complete cycle of vibration to pass a given point. Unit of time period is second (s)

8. Types of Vibratory Motion

9. Free vibration   occurs when a mechanical system is set in motion with an initial input and allowed to vibrate freely.   Examples of free vibration are oscillations of a pendulum about a vertical equilibrium position and a motion of a vehicle suspension system after the vehicle encounters a pothole.. The mechanical system vibrates at one or more of its natural frequencies and damps down to motionlessness. Free Vibratory Motion

10. Forced Vibration Forced vibrations occur when the object is forced to vibrate at a particular frequency by a periodic input of force.

11.  When the energy of a vibrating system is gradually dissipated by friction and other resistances, the vibrations are said to be damped. Damped vibration

12. INSTRUMENTS used FOR MEASUREMENT of VIBRATION VIBROMETER VIBRATION ANALYSER

13. Simple Harmonic Motion Any vibrating system where the restoring force is directly proportional to the negative displacement . Any object exhibiting this is called a simple harmonic oscillator (SHO)

14. Restoring Force (F) Force exerted when away from equilibrium Directly proportional to the displacement (x) F = - kx k – spring constant

15. Mass Sparing System The mass spring system works on the application of Vibration as well simple harmonic motion .

16. Therefore, we can use the period and frequency of a particle moving in a circle to find the period and frequency:

17. Pendulum A  simple pendulum  is  defined  as an object that has a small mass, also known as the  pendulum  bob, which is suspended from a wire or string of negligible mass. When displaced, a  pendulum  will oscillate around its equilibrium point due to momentum in balance with the restoring force of gravity.

18. Wave Wave – a disturbance that transfers energy the energy transferred through a wave can be carried from the disturbance, through the wave, to another object Ex: wind gives energy (a disturbance), creating waves on an ocean, and the ocean carries that energy to a boat, and the energy rocks the boat up and down the energy from the disturbance is transferred through a medium

19. Mechanical Types of Waves Transverse waves Longitudinal Waves

20. Transverse Waves Transverse waves – waves whose mediums move a right angles (perpendicular) to the direction of overall wave travel -- if the wave below moves left-to-right, the medium will move up-and-down -- like whipping a rope Parts of a Transverse Wave Crest – the “upper higher amplitude” parts of the transverse wave Trough – the “Lower higher amplitude” parts of the transverse wave Crest Trough

21. Longitudinal Waves Longitudinal Waves – waves whose mediums move in the same direction as overall wave travel -- like squeezing and releasing a slinky spring -- longitudinal waves are often called compression waves Parts of a Longitudinal wave Compressions – areas where the molecules in the medium are tightly squeezed together Rarefactions – areas where the molecules in the medium are spread apart

22. Wave Properties Despite the different types of waves, all waves share the same basic properties: amplitude wavelength frequency speed When figuring out these properties on either longitudinal or transverse waves, it is necessary to remember the following: Crests on a transverse wave are equal to compressions on a longitudinal wave Troughs on a transverse wave are equal to rarefactions on a longitudinal wave

23. Interference Interference – when two or more waves meet in the same medium Constructive Interference – when two waves add up to make a larger wave amplitude Constructive Destructive Interference – when waves add up to make a smaller or zero wave amplitude (cancel each other out) Destructive

24. Constructive Interference

25. Destructive Interference

26. Resonance Resonance – occurs when vibrations travelling through an object match the object’s natural frequency Also occurs when one object vibrates another object without touching it

27. Result of Resonance Glass shattering Tacoma Narrows Bridge collapsing

28. Reflection Reflection occurs when a wave strikes an object and bounces off of it. All types of waves can be reflected The angle of incidence of a wave is always equal to the angle of reflection.

29. Refraction Refraction – the bending of a wave caused by a change in its speed as it moves from one medium to another

30. Diffraction Spreading of waves that happen when it passes through a narrow opening or when it passes round a small obstacle along its path.