Credit: Eden, Janine and Jim
License: CC BY-NC 3.0
Periodic motion is any motion that repeats itself. This chapter covers a particular case of such called simple harmonic motion - for motion back and forth in a straight line such as a pendulum. The properties of simple harmonic motion include the basics of wave properties.
- The projection of uniform circular motion onto a straight line is called simple harmonic motion(SHM); it is the simplest form of periodic motion.
- An object performing SHM must have a restoring force upon it that seeks to return it to its equilibrium position which is directly proportional to the object’s displacement; that is F=−kx where the negative sign indicates that the restoring force and displacement are oppositely directed and kis a constant of proportionality.
- The period T for a mass m on a spring is T=2πmk−−−√ where the spring is constant is k.
- The frequency is f=1T or f=12πkm−−−√
- The period T of a simple pendulum of length L is T=2πLg−−√ where the gravitational acceleration is g.
- Waves transmit energy but not mass.
- Longitudinal waves occur when vibrations are parallel to wave direction.
- Transverse waves occur when vibrations are perpendicular to the wave direction.
- Reflection occurs when waves bounce off one medium back into the medium they originated from.
- Refraction occurs when waves bend entering one medium from the other.
- Diffraction occurs when waves spread out and when waves bend behind objects.