1 / 19

Physics Notes Ch 11

Physics Notes Ch 11 . 11 - 1 Simple Harmonic Motion. Vibration/Oscillation – Movement about an equilibrium position Periodic - Repeats itself back and forth over the same motion Equilibrium Position – Position where the net force is zero on an object. Spring F = -kx

amyreed
Download Presentation

Physics Notes Ch 11

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Physics Notes Ch 11

  2. 11 - 1 Simple Harmonic Motion • Vibration/Oscillation – Movement about an equilibrium position • Periodic - Repeats itself back and forth over the same motion • Equilibrium Position – Position where the net force is zero on an object

  3. Spring F = -kx • Spring constant – Force required to stretch a spring a unit of length • Displacement – Distance of disturbance from it’s equilibrium position

  4. Cycle – One complete repetition of periodic motion. May start in any location. • Period – Length of time it takes for a cycle to complete. It is the inverse of frequency. • Amplitude – The maximum distance from the equilibrium that occurs in periodic motion. • f = 1/T T = 1/f

  5. Simple Harmonic Motion - vibrating system in which the restoring force is directly proportional to the negative of the displacement

  6. Springs • Why does spring oscillation stop? • Friction converts mechanical energy into thermal energy • Period and frequency not effected by amplitude • T=2m/k

  7. 11-4 The Simple Pendulum • Period of oscillation does not depend on amplitude • Force diagram - Fig 11-12 pg. 319 • Pendulum motion does not depend on the mass, ONLY length of string. • Period of a pendulum T=2L/g • Clocks – Must supply energy to the pendulum to maintain its swing - Falling weights

  8. 11-6 Resonance • Natural frequency - frequency of a vibrating system when it is set into motion • Resonance – A large increase in the amplitude of a vibration when a force is applied at the natural frequency of the medium or object. • Swing set – must pump legs at specific times during natural frequency of swing. Depends on length of swing. Push every other time at _ resonant frequency • Vibrations produce sounds at natural frequency

  9. Resonance – Good and Bad effects – Radio station tune to resonance frequency, bridges, earthquakes • Tacoma Narrows Bridge - Long (2800 ft) and narrow (40 ft) bridge. Wind caused oscillations. Very flexible structure. Wind was perpendicular to bridge, causing vortices to form creating a translating (twisting) motion on the bridge deck. Close to the natural frequency of the bridge (amplified). • Loma Prieta Earthquake – Bay Mud increased amplitude of vibrations causing more damage. Fire caused by broken gas lines, not water due to broken water lines. • Website Demo

  10. 11 - 7 Waves • Waves – The movement of energy from one place to another without any accompanying matter • Pulse wave – dominos, spring demo • Periodic wave – All pulses have the same size and shape repeats itself over a distance of one wavelength and a time of one period.

  11. Rope waves • pg. 325 Fig 11-23 • Crest – Peak of wave motion • Trough – Valley of wave motion

  12. Wavelength () – Distance that a wave pattern repeats. • Frequency (f) – Number of times a periodic motion repeats in a unit of time. Inverse of period. • Amplitude (A) - Maximum height of a crest or depth of a trough relative to the equilibrium level • Speed = wavelength X frequency V = f

  13. 11-8 Transverse and Longitudinal Waves • Transverse wave – vibration of medium is perpendicular to the motion of the wave. • Longitudinal wave – Vibration of the medium is in the same direction as the motion of the wave. • Spring ( Fig 11-24 pg. 326) – • Vertically – Transverse • Horizontally –Longitudinal

  14. Transverse waves cannot exist in fluid • Earthquake waves • Three types – Surface waves, P & S waves (through interior) • Earth radius 6400 km (4000 miles) • Waves partially reflected through different regions and change speeds with physical conditions (elasticity and density)

  15. Longitudinal waves – P waves (compression) caused by expansion and contraction of rocks near surface. Pass through solids, liquids and gasses. • Transverse waves - S waves (Shear waves) rolling motion. Most damaging. • Locate epicenter of earthquake by triangulation

  16. 11-11 Reflection and Superposition • Reflection - return pulse returns inverted • Superposition – The combination of two or more waves at a location in space (add together) • Waves pass as if the other was not there – pebbles in a pond • Interference - The superposition of two waves

  17. In Phase - Produce crests at the same time and troughs at the same time. Same wavelength and frequency. • Constructive interference - Crest meets crest, trough meets trough. Amplitude increases. • Destructive interference - Crest meets trough. Amplitude decreases. • Diffraction - The spreading of waves passing though a barrier. Depends on size of opening and wavelength. Overhead.

  18. 11-12 Standing Waves • Standing Waves - Confined periodic wave. Appears to stand still in the horizontal direction. • Standing wave - The inference pattern produced by two waves of equal amplitude and frequency traveling in opposite directions. • Node - One of the positions in a standing wave where there is no movement, amplitude equals zero. • Antinode - One of the positions in a standing wave where there is maximal movement, amplitude is a maximum.

  19. Distance between adjacent nodes or adjacent antinodes is one-half wavelength • Spring Demo • Fundamental frequency - Lowest resonant frequency for an oscillating system. Also has longest wavelength. • Harmonic - A frequency that is a whole number multiple of the fundamental frequency. • Spring demo

More Related