Chapter 8: SHM (damping) Flashcards
What are the energy changes of an oscillator?
-potential
-kinetic
-potential
What does potential energy include?
gravitational & elastic
How often are the changes in energy?
PE —> KE —-> PE
every half-cycle
Where is KE highest?
at the equilibrium position
Where is potential highest?
at top/bottom
What is damping?
the loss of energy from an oscillating system to the environment due to
dissipative forces
What are examples of dissipative forces?
friction
viscous forces
eddy currents
What is light damping?
The system oscillates about the equilibrium position with decreasing amplitude over
a period of time.
What is critical damping?
- the system does not oscillate
- damping is just adequate such that the system
returns to its equilibrium position in the shortest possible time.
What is heavy damping?
-object never oscillates but returns to its
equilibrium position very very slowly.
What is a free oscillation?
an object whose motion is not subjected to an external periodic driving force
(system oscillates at natural frequency)
What is a forced oscillation?
-undergoes forced oscillations
-subject to an input of energy from an external periodic driving force
-oscillates at the frequency of the driving force
What is resonance?
the amplitude of a system undergoing forced oscillations
increases to a maximum
-occurs when the frequency of the periodic driving force
==to the natural frequency of the system.
What are the effects of damping?
- resonant frequency decreases
-sharpness of resonant peak decreases
-amplitude of forced oscillation decreases
What are examples of useful purposes of resonance?
-oscillation of a child’s swing
-tuning of musical instruments
-tuning of radio receiver
-microwave
-MRI
-seismography
How does a microwave work?
produces microwaves of a frequency which is
equal to the natural frequency of water molecules
-causing the water molecules in the food to
vibrate more violently
- this generates heat to cook the food but the glass and paper containers do
not heat up as much
What are examples of the destructive nature of resonance?
-Tarcoma Narrows Bridge
-High pitched sounds can shatter glass objects
What is simple harmonic motion?
-oscillations in which the acceleration (or restoring force) is always proportional to and opposite in direction to the displacement from a certain equilibrium position
