# Shared Flashcard Set

## Details

Simple Harmonic Motion
N/A
47
Physics
Not Applicable
10/16/2012

Term
 MEASURING OSCILLATIONS
Definition
 One full cycle of motion is from maximum height at one side to maximum height on the other side then back to the first side.
Term
 LOWEST POINT OF AN OSCILLATION
Definition
 Is the equilibrium point; in motion the object is said to oscillate about equilibrium
Term
 DISPLACEMENT OF THE OBJECT
Definition
 From equilibrium changes during motion: decreases as returns to equilibrium; reverses and increases moving away from equilibrium in opposite direction; decreases as it returns to equilibrium; increases as it moves away from equilibrium towards starting position
Term
 AMPLITUDE
Definition
 Maximum displacement of the oscillating object from equilibrium
Term
 FREE OSCILLATIONS
Definition
 Constant amplitude with no frictional forces
Term
 TIME PERIOD
Definition
 Time for one complete cycle of oscillations
Term
 FREQUENCY
Definition
 Number of cycles per second
Term
 ANGULAR FREQUENCY
Definition
 2∏ / T
Term
 PHASE DIFFERENCE
Definition
 If two things do not oscillate correspondingly they have a phase difference because they are not in phase.    Phase difference in radians  = 2∏♦t / T
Term
 PHASE DIFFERENCE IN DEGREES
Definition
 2∏ radians  = 360º   so phase difference = 360 x ♦t / T
Term
 PRINCIPLES OF SIMPLE HARMONIC MOTION
Definition
 Oscillating objects speed up as it returns to equilibrium; slows down when it moves away from equilibrium
Term
 VARIATION OF VELOCITY WITH TIME
Definition
 Gradient of the displacement time graph
Term
 WHEN IS VELOCITY GREATEST?
Definition
 When gradient of displacement time graph is greatest; at zero displacement
Term
 VARIATION OF ACCELERATION WITH TIME
Definition
Term
 WHEN IS ACCELERATION GREATEST?
Definition
 When gradient of velocity time graph is greatest so when velocity is zero and displacement is maximum in opposite direction
Term
 WHEN IS ACCELERATION ZERO?
Definition
 When displacement is zero. When gradient of velocity time graph is zero
Term
 ACCELERTATION AND DISPLACEMENT
Definition
 Acceleration is always in the opposite direction to the displacement (opposite signs)
Term
 SIMPLE HARMONIC MOTION
Definition
 The oscillating motion in which the acceleration is proportional to the displacement and always in the opposite direction to the displacement    acceleration = -constant x displacement   a = -(2∏f)2x
Term
 WITH SINE AND CO SINE CURVES
Definition
Term
 RESTORING FORCE
Definition
 Resulting force acting toward the equilibrium position ALWAYS
Term
 RESTORING FORCE, ACCELERATION AND DISPLACEMENT
Definition
 If the restoring force is proportional to the displacement to equilibrium, acceleration will also be equal to displacement (always towards equilibrium) THE OBJECT OSCIALLATES WITH SIMPLE HARMONIC MOTION
Term
 TWO STRETCHED SPRINGS AND A TROLLEY
Definition
 Half cycel can be recorded using a ticker tape attatched to one end of the trolley. When trolley is released, the ticker timer prints dots on the tape at 50 dots per second. Graph of displacement against time can be plotted which can measure time period   Motion sensor linked to computer can record osciallting motion
Term
 CHANGING THE FREQUENCY OF THE OSCILLATIONS OF A LOADED SPRING
Definition
 Adding extra mass - increases interia; at certain displacement trolley would be slower without extra mass. INCREASING TIME FOR EACH CYCLE Weaker springs - Restoring force would be less at any given displacement , so INCREASES TIME FOR EACH CYCLE OF OSCILLATION
Term
 FREE OSCILLATIONS
Definition
 An object oscillates with a constant amplitude because there is no friction force acting on it.   Only forces acting on it combine to form the restoring force. If friction was present, the amplitude of oscillations would gradually decrease and stop Friciton is usually present even if you can't see the change in amplitude after one cycle
Term
 ENERGY CHANGES
Definition
 At maximum displacement, velocity is 0 so potential energy is at it's maximum and kinetic energy is 0    At 0 displacement, velocity is at it's maximum so potential energy is 0 and kinetic energy is maximum
Term
 IF FRICTION IS ABSENT
Definition
 Total energy of system remains constant and equal to maximum potential energy
Term
 A
Definition
 Amplitude
Term
 DAMPED OSCILLATIONS
Definition
 When dissipative forces are present
Term
 DISSIPATIVE FORCES
Definition
 Dissipate the energy of the system to the surroundings as thermal energy.
Term
 LIGHT DAMPING
Definition
 Time period is independent of amplitude.  Each cycle takes the same length of time as the oscillations die Amplitude gradually decreases reducing by the same fraction each cycle.
Term
 CRITICAL DAMPING
Definition
 Just enough to stop the system oscillating after it has been displaced and released from equilibrium.  Oscillating object returns to equilibrium in shortest possible time without over shooting. Important in mass spring systems such as vehicle suspension.
Term
 HEAVY DAMPING
Definition
 Damping is so strong that the displaced object returns to equilibrium much more slowly than if it critically damped. No oscillating motion occurs. e.g mass on a spring in thick oil.
Term
 CAR SUSPENSION SYSTEM
Definition
 A coiled spring near each wheel, between wheel axle and car chassis.  When wheel is jolted , the srping smoothes out the force on the jolts. The oil damper fitted with each spring prevents the chassis from bouncing up and down too much. Flow of oil through valves in the piston of each damper provides frictional force that damps oscillating motion. Dampers ensure chassis returns to equilibrium in the shortest possible time - so close to critical damping
Term
 FORCED OSCILLATIONS
Definition
 E.g pushing someone on a swing
Term
 PERIODIC FORCE
Definition
 Pushes on a swing are an example.    Force that varies regularly in magnitude with a definate time period
Term
 NATURAL FRQUENCY
Definition
 When a system oscillates without a periodic force being applied to it
Term
 AS APPLIED FREQUENCY REACHES NATURAL FRQUENCY OF THE MASS - SPRING SYSTEM
Definition
 The amplitude of oscillations of the objects increase more and more    Phase difference between the displacement and periodic force increases from zero to 1/2∏ at the natural frequency
Term
 RESONANCE
Definition
 Applied frequency is equal to natural frequency of mass spring system Amplitude of oscillations become very large; lighter the damping, the larger the amplitude becomes Phase difference between displacement and the periodic force is 1/2∏    Periodic force is in phase with the velocity of the oscillating object.
Term
 APPLIED FRQUENCY GREATER THAN NATURAL FREQUENCY
Definition
 Amplitude of oscillations decrease more and more Phase difference between displacement and periodic force increases from 1/2∏  until it is ∏ out of phase with the periodic force.
Term
 WHEN IS THE AMPLITUDE GREATEST
Definition
 When applied frequency is equal to natural frequency providing damping is light   here:    applied frequency of periodic force = natural frequency of a system
Term
 OSCILLATING SYSTEM WITH LITTLE OR NO DAMPING AT RESONANCE
Definition
 Applied frequency of periodic force = natural frequency of system
Term
 AT RESONANCE
Definition
 The periodic force acts on the object at the same point in each cycle causing the amplitude to increase to a maximum value limited only by damping.    Max amplitude, energy supplied by periodic force is lost at the same rate because of the effects of damping
Term
 APPLIED FREQUENCY AT RESONANCE
Definition
 Resonant frequency = natural frequency when there is little/no damping   The lighter the damping, the closer the resonant frequency to natural   Resonance occurs at a slightly lower frequency than natural
Term
 PENDULUMS OF THE SAME LENGTH
Definition
 If one pendulum is displaced, the other of the same length is forced to oscillate too and responds much more than if it were at any other length.  It has the same time period so same natural frequency so oscillate in resonance. Response of other lengths depends on how close they are to initial pendulum.
Term
 BRIDGE OSCILLATIONS
Definition
 If wind speed means the periodic force is equal to natural frequency, resonance can occur in absence of damping   e.g collapse bridge
Term
 STEADY TRAIL OF PEOPLE ON A BRIDGE
Definition
 With insufficient damping, people in step with each other can cause resonant oscillations
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