Periodic Motion Motions that repeat in a regular cycle. - PowerPoint PPT Presentation

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Periodic Motion Motions that repeat in a regular cycle.

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Periodic Motion Motions that repeat in a regular cycle. Simple Harmonic Motion During motion, object has one point where the net force is zero (equilibrium). – PowerPoint PPT presentation

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Title: Periodic Motion Motions that repeat in a regular cycle.


1
Periodic MotionMotions that repeat in a regular
cycle.
2
Simple Harmonic Motion
  • During motion, object has one point where the net
    force is zero (equilibrium).
  • Whenever the object if pulled away from
    equilibrium, the net force becomes non-zero and
    works to pull the object back to equilibrium.
  • The force needed to restore equilibrium is
    directly proportional to the displacement of the
    object.

3
  • Period (T) - time for the object to complete one
    cycle of motion.
  • Amplitude - maximum distance that the object
    moves away from equilibrium.

4
  • Hookes Law - The force exerted by a spring is
    equal to the spring constant times the distance
    the spring is compressed or stretched from its
    equilibrium point. F -kx
  • Potential energy in a stretched or compressed
    spring is equal to one half the product of the
    spring constant and the square of the
    displacement. PEsp ½ kx2

5
Period of a Pendulum is equal to two times pi
times the square root of the length of the
pendulum divided by acceleration due to gravity.
T 2?vl/g
6
Resonance - the increase in the amplitude of a
vibrating or oscillating object due to the
application of small forces during regular
intervals.
  • Pumping your legs when swinging.
  • Wind causing the Tacoma Narrows bridge collapse.

7
Wave - a disturbance that carries energy through
matter or space (matter is not transferred).
8
  • Transverse Wave - wave pulse (disturbance)
    vibrates perpendicular to the direction of the
    waves motion.
  • Longitudinal Wave - wave pulse (disturbance)
    vibrates parallel to the direction of the waves
    motion.

9
Wave Measurements
  • Speed (v) - the speed of a wave pulse is equal to
    the displacement of the wave peak divided by the
    amount of time. v ?d / ?t
  • Amplitude (A) - the maximum displacement of the
    wave from its position of rest. For waves that
    have the same speed, the rate of energy transfer
    is proportional to the square of the amplitude.
  • Wavelength (?) - the shortest distance between
    points where the wave pattern repeats itself.
  • Period (T) - the time it takes wave to complete
    one cycle (wavelength).
  • Frequency (f) - the number of complete
    oscillations it makes each second.

10
  • The frequency of a wave is equal to the
    reciprocal of the period. f 1 / T
  • The wavelength is equal to velocity divided by
    the frequency. ? v / f

11
Wave Behavior
  • Incident wave - initial wave that strikes a
    boundary.
  • Reflected wave - returning wave after the
    collision of the incident wave with a boundary.

12
Principle of Superposition
  • When two waves exist in the same place in the
    medium at the same time the displacement of the
    medium is equal to sum of the two individual wave
    displacements.

13
Wave Interference - the result of the
superposition of two or more waves.
  • Destructive - when two waves with opposite
    amplitudes meet. If these are equal amplitudes
    then the point that they meet (node) does not
    move.
  • Constructive - when two waves with amplitudes in
    the same direction meet. Produces an a point
    where the largest amount of displacement occurs
    (antinode).

14
  • Standing waves are produced through the
    constructive and destructive interference of
    waves. Increasing the frequency of oscillations
    increases the number of nodes and antinodes.

15
Waves in 2 Dimensions
  • When an incident wave strikes a barrier it will
    be reflected. The angles formed between the
    incident ray and the normal (draw line that is
    perpendicular to the barrier) and the reflected
    ray and the normal are equal.

16
  • Refraction is the change in direction of a wave
    at the boundary between two different media.
  • For example waves approaching shore will always
    have the same frequency, however, their
    wavelength and velocity decreases. This will
    cause a change in direction between these two
    media.
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