13. Oscillations Flashcards

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1
Q

What happens it an object is experiencing simple harmonic motion?

A
  • It experiences a restoring force which acts towards the centre of equilibrium.
  • Its force is directly proportional to the object’s distance from equilibrium.
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2
Q

What is amplitude?

A

The maximum displacement of an oscillating system

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3
Q

What is time period?

A

Time take for one full cycle of an oscillating system.

e.g.
Equilibrium to amplitude.
Then amplitude to equilibrium.

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4
Q

What is the restoring force?

A

A force that acts towards the equilibrium.

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5
Q

What is true about the acceleration of an object experiencing SHM?

A

It’s acceleration is directly proportional to is displacement and is in the opposite direction.

a = -ω²x

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6
Q

What is angular velocity?

A

The angle an objects moves through per unit time.

ω = 2πf

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7
Q

What effect the time period of these simple harmonic systems?

  • Simple pendulum
  • Mass-spring system
A

Simple pendulum: mass and length of spring.

  • Mass-spring system:
    mass and spring constant.
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8
Q

Describe the graph of displacement against time of a SHsystem.

A

Sinusoidal

- starting at (+)amplitude.

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9
Q

Describe the graph of velocity against time of a SHsystem.

A

Sinusoidal
- starting at 0

(its the gradient function of dis-time)

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10
Q

Describe the graph of acceleration against time of a SHsystem.

A

Sinusoidal
- starting at (-)amplitude.

(its the gradient function of velo-time)

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11
Q

What is resonence?

A

Where the amplitude of an oscillating system increases due to gaining an increased amount of energy from the driving force.

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12
Q

When does resonance occur?

A

When the driving force is equal to the natural frequency of the system.

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13
Q

How do you decrease the effects of resonance?

A

Dampening.

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14
Q

What is dampening?

A
  • Where a force acts on an oscillating system and energy is lost from the system to its environment.
  • Leading to a reduced amplitude.
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15
Q

When can oscillating systems lose/gain energy?

A

When an external force acts on it.

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16
Q

What is true of an undamped system?

A
  • There are no external forces acting.
  • No energy is lost to the environment.
  • Total energy of the system remains constant.
17
Q

Describe the change in energy of a SHsystem.

A
  • At amplitude the system has maximum potential energy.
  • As moves to equilibrium, PE is converted to kinetic energy.
  • At centre of oscillation KS is at a maximum.
18
Q

What are free vibrations?

A
  • When there is no external force that is continuously acting on a system.
  • Thus the system oscillates at its natural frequency.
19
Q

What are force vibrations?

A
  • When a system experiences an external driving force which causes it to oscillate.
  • Its frequency is known as the driving frequency.
20
Q

What are the three types of damping?

A
  • Over.
  • Critical.
  • Under.
21
Q

What is under damping?

A
  • Where the amplitude gradually decreases by small amounts each oscillation.
  • Graph of diminishing sinusoidal wave.
22
Q

What is critical damping?

A
  • Where the amplitude reduces to zero in the shortest possible time without oscillating.
  • Starts at maximum and curves to zero rapidly.
23
Q

What is over-damping?

A
  • Where the amplitude reduces slower than critical damping but without any additional oscillations.
  • Starts at zero and curves to zero over time.
24
Q

What happens to the amplitude once the degree of dampening increases?

A

It decreases.

25
Q

What is a ductile material?

A

One that can undergo a large amount of plastic deformation before fracturing.

26
Q

Why can a ductile material be used in dampening?

A
  • it can reduce the amplitude of oscillation
  • because energy is used to defor the material.
  • decreasing the KE of the system.
  • so decreasing the amplitude of oscilation.