Chapter 8: SHM (damping)

Question 1

What are the energy changes of an oscillator?

Answer 1

-potential
-kinetic
-potential

Question 2

What does potential energy include?

Answer 2

gravitational & elastic

Question 3

How often are the changes in energy?

Answer 3

PE —> KE —-> PE
every half-cycle

Question 4

Where is KE highest?

Answer 4

at the equilibrium position

Question 5

Where is potential highest?

Answer 5

at top/bottom

Question 6

What is damping?

Answer 6

the loss of energy from an oscillating system to the environment due to
dissipative forces

Question 7

What are examples of dissipative forces?

Answer 7

friction
viscous forces
eddy currents

Question 8

What is light damping?

Answer 8

The system oscillates about the equilibrium position with decreasing amplitude over
a period of time.

Question 9

What is critical damping?

Answer 9

• the system does not oscillate
• damping is just adequate such that the system
  returns to its equilibrium position in the shortest possible time.

Question 10

What is heavy damping?

Answer 10

-object never oscillates but returns to its
equilibrium position very very slowly.

Question 11

What is a free oscillation?

Answer 11

an object whose motion is not subjected to an external periodic driving force
(system oscillates at natural frequency)

Question 12

What is a forced oscillation?

Answer 12

-undergoes forced oscillations
-subject to an input of energy from an external periodic driving force
-oscillates at the frequency of the driving force

Question 13

What is resonance?

Answer 13

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.

Question 14

What are the effects of damping?

Answer 14

• resonant frequency decreases
  -sharpness of resonant peak decreases
  -amplitude of forced oscillation decreases

Question 15

What are examples of useful purposes of resonance?

Answer 15

-oscillation of a child’s swing
-tuning of musical instruments
-tuning of radio receiver
-microwave
-MRI
-seismography

Question 16

How does a microwave work?

Answer 16

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

Question 17

What are examples of the destructive nature of resonance?

Answer 17

-Tarcoma Narrows Bridge
-High pitched sounds can shatter glass objects

Question 18

What is simple harmonic motion?

Answer 18

-oscillations in which the acceleration (or restoring force) is always proportional to and opposite in direction to the displacement from a certain equilibrium position