AP Physics 1 Review Session 4 Oscillations, Waves, & Electricity

Simple Harmonic Motion Objects oscillate with a constant period/frequency As the position from the equilibrium position increases, the restoration force increases Energy constantly changes from potential to kinetic

Key Terms

Graphs of SHM

Equation of SHM

The simple pendulum A pendulum is a vibrating system in which the motion is very apparent. Consider a simplified model of a pendulum system that has a compact object (a bob) at the end of a comparatively long and massless string and that undergoes small-amplitude vibrations. This idealized system is called a simple pendulum. © 2014 Pearson Education, Inc.

The simple pendulum Two objects interact with the bob of the pendulum. The string S exerts a force that is always perpendicular to the path of the bob. Earth exerts a downward gravitational force. © 2014 Pearson Education, Inc.

Examples of SHM Pendulums Mass-Spring Systems

Mechanical Waves Waves that travel through matter Wave Speed

Two kinds of waves © 2014 Pearson Education, Inc.

Superposition principle for waves The process in which two or more waves of the same frequency overlap is called interference. Places where the waves add to create a larger disturbance are called locations of constructive interference. Places where the waves add to produce a smaller disturbance are called locations of destructive interference. © 2014 Pearson Education, Inc.

Loudness and intensity Loudness is determined primarily by the amplitude of the sound wave: the larger the amplitude, the louder the sound. Equal-amplitude sound waves of different frequencies will not have the same perceived loudness to humans. To measure the loudness of a sound, we measure the intensity: the energy per unit area per unit time interval. © 2014 Pearson Education, Inc.

Pitch, frequency, and complex sounds Pitch is the perception of the frequency of a sound. Tuning forks of different sizes produce sounds of approximately the same intensity, but we hear each as having a different pitch. The shorter the length of the tuning fork, the higher the frequency and the higher the pitch. Like loudness, pitch is not a physical quantity but rather a subjective impression. © 2014 Pearson Education, Inc.

Fundamental and harmonics The lowest frequency of a complex wave is called the fundamental. Higher-frequency components that are whole-number multiples of the fundamental are called harmonics. We usually identify the pitch as the fundamental frequency. The complexity of the waveform (the number of harmonics) contributes to the quality of the sound we associate with specific instruments. © 2014 Pearson Education, Inc.

Beat and beat frequencies Two sound sources of similar (but not the same) frequency are equidistant from a microphone that records the air pressure variations due to the two sound sources as a function of time. © 2014 Pearson Education, Inc.

Beat and beat frequencies © 2014 Pearson Education, Inc.

Standing waves on strings You shake the end of a rope that is attached to a fixed support. At specific frequencies, you notice that the rope has large-amplitude sine-shaped vibrations that appear not to be traveling. © 2014 Pearson Education, Inc.

Standing waves on a string The lowest-frequency vibration of the rope is one up-and-down shake per time interval: This frequency is called the fundamental frequency. © 2014 Pearson Education, Inc.

Standing wave vibration frequencies in open-open pipes © 2014 Pearson Education, Inc.

Standing wave vibration frequencies in open-closed pipes © 2014 Pearson Education, Inc.

The Doppler effect: Putting it all together When you hear the sound from a horn of a passing car, its pitch is noticeably higher than normal as it approaches, but noticeably lower than normal as it moves away. This phenomenon is an example of the Doppler effect. The Doppler effect occurs when a source of sound and an observer move with respect to each other and/or with respect to the medium in which the sound travels. © 2014 Pearson Education, Inc.

Doppler effect for the source moving relative to the medium © 2014 Pearson Education, Inc.

Electrical Force Directly related to product of charge Inversely related to the square of the distance between them

Contemporary model for electric charge Two objects start as neutral—the total electric charge of each is zero. During rubbing, one object gains electrons and becomes negatively charged. The other object loses an equal number of electrons and with this deficiency of electrons becomes positively charged. © 2014 Pearson Education, Inc.

Current Moving charges Measured in Amperes

Electrical Resistance

Ohm’s Law

Joule’s Law

Kirchhoff’s Rules

Series resistance © 2014 Pearson Education, Inc.

Parallel resistance © 2014 Pearson Education, Inc.