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# MCAT Physics

### Ch. 8 Periodic motion, Waves, Sound

Question | Answer |
---|---|

Hooke's Law | F=-kx |

acceleration of a spring with constant k and mass m, having been displaced x meters | a=-w^2x, w=angular frequency. w=2pif=(k/m)^1/2 w is measured in radians per second, |

what does frequency/angular frequency depend on | the spring constant and the mass attached to the spring, but not on the displacement of the spring |

kinetic and potential energy for springs | U=1/2kx^2 K=1/2mv^2 |

restoring force of pendulum | F=-mgsin(theta) |

angular frequency of pendulum | w=2pif=(g/L)^1/2 only the acceleration of gravity and the length of the pendulum affect angular frequency |

pendulum max potential energy | U=mgh h is the vertical height difference between the pendulum's mass in the equilibrium position and mass at the given angular displacement |

longitudinal waves | particles of the wave oscillate along the direction of travel of the wave motion; the wave particles are oscillation along the direction of energy transfer. |

transverse waves | particles are oscillating perpendicular to the direction of energy transfer |

displacement of particle in a wave | y=Ysin(kx-wt) Y is amplitude, k is wave number, w is angular frequency |

speed of wave v | v=(freq.)(lambda) |

wave number and angular frequency | k=(2pi)/lambda w=2pif=(2pi)/T |

what is speed of sound proportional too | inversely proportional to the square root of density but directly proportional to the square root of the bulk modulus. |

Intensity | I=P/A SI units of W/m^2 A is surface area, also expressed as P=IA |

What is intensity proportional too | the square of the amplitude. Doubling amplitude produces wave that is 4 times as intense. Intensity also related to distance from the source of sound wave. |

decibels equation | B=10log(I/I.) I.=threshold of hearing 1x10^-14 W/m^2 ratio of two intensities can be found by Bf=Bi+log(If/Ii) where If/Ii is the ration of the final intensity of the initial intensity |

doppler shifts | if source and detector moving toward each other, perceived freq f' is greater than actual frequency f, if moving away perceived frequency f' is less than actual freq. |

standing wave equations | lambda=(2L/n) f=(nv/2L) n=1,2,3,... |

what is the fundamental frequency | the lowest frequency (longest wavelength) of a standing wave that can be supported in a given length of string |

pipes and standing waves (nodes and anodes) | if the end is open, it will support an antinode, if it is closed, it will support a node |

open pipe wave equations | lambda=(2L/n) n=1,2,3,... f=v/f, f=(nv/2L) |

closed pipe wave equations | lambda=(4L/n) n=1,3,5,.... f=(nv/4L) |