9 February 2013
1. A wiggle in time is a Vibration
A.)Vibration- An oscillation or repeating back and forth motion, about an equilibrium position.
2. A vibration cannot exist in one instance, but needs time to move back and forth. 3. A wiggle in space and time is a Wave.
A.)Wave- a disturbance that repeats regularly in space and time and that is transmitted progressively from one place to the next with no actual transport of matter.
4. A wave cannot exist in one place, but must extend form one place to another. A.) Light and Sound are examples that move through space as waves and are forms of energy. II- Vibration of Pendulum (25.1)
1. Pendulums swing back and forth with such regularity that they have long been used to control motion of clocks.
2. The time a pendulum swings back and forth does not have to do with the mass or the distance it swings, the Period ( time it takes to swing back and forth) depends only on the length of Pendulum and the acceleration of gravity. A.)Period-The time required for a pendulum to make one to and from swing. In general the time required to complete a single cycle.
3. A longer one swings a longer period than a shorter one. A.) Longer- Swings back and forth slower – less frequently Shorter- Swings Fast- more frequent due to its size
4. Ex.- Long legged person has slower stride because covers more area while short legged people have to walk faster.
III- Wave Description (25.2) 1. Simple Harmonic Motion- periodic motion in which acceleration is proportional to the distance from an equilibrium position and is directed toward that equilibrium position. 2. The restoring force is proportional to the displacement from equilibrium 3. The component of weight that restores a displace pendulum to its equilibrium position is directly proportional to the pendulums displacement (for small angles)- like- a weight attached to a string. 4. When the conveyor bet is stationary the sand traces out a straight line. When the conveyor belt is moving at a constant seed the sand traces out a special curve known as a sine curve. 5. Sine Curve A.) A sine curve is a pictorial representation of a wave B.) The highest points are called crests C.) The low points are referred to as troughs.. D.) The straight dashed line represents the “home” position or the midpoint of the vibration E.) Amplitude refers to the distance from the midpoint to the crest or trough of the wave. F.) The amplitude = the maximum displacement from equilibrium 6. Wave lengths
A.) Wavelength- the distance from the top of one crest to the other crest or the distance between successive identical parts of the wave
B.)The wave lengths of waves at the beach are measured in meters, the wavelengths of ripples in a pond in centimeters and the wavelengths of light in billionths of a meter (nanometers) 7. Frequency A.) Frequency- how often a vibration occurs
B.) the frequency of a vibrating pendulum or an object on a spring specifies the number of back and forth vibrations it makes in a give time (usually one second)
C.) A complete back and forth vibration is one cycle. If it occurs in one second the frequency is one vibration per second or one cycle per second. 8. Hertz A.) the unit of frequency is hertz. B.) a frequency of one cycle per second is 1 hertz
C.) higher frequencies are measured in kilohertz (kHz-Thousands of hertz)
D.) Higher frequencies than kHz- MHz- mega hertz- millions of hertz or gigahertz-GHz- billions of hertz
E.)Am radio waves broadcasted in KHZ FM radio waves broadcasted in MHZ G.) Radar and microwave ovens operate at gigahertz GHZ H.) A station at 960 KHZ on AM broadcasts radio waves that have a frequency of 96,000 vibrations per second. I.) A station 101 MHZ on FM broadcast the radio waves that have a frequency of 101,000,000 hertz.