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Physics Unit 1 > Chapter 5: Oscillations > Flashcards

Chapter 5: Oscillations Flashcards

0
Q

Define free oscillation

A

An object oscillates at its natural frequency

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1
Q

Give 3 examples of free oscillations

A
  1. Vibrations of a guitar string when you pluck it 2. Vibrations of a tuning fork when you strike it 3. Oscillation of a child in a swing
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2
Q

Define oscillation

A

An object moves back and forth repeatedly on either side of its equilibrium position

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3
Q

Define displacement

A

The distance an object has moved from its equilibrium position

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4
Q

Define amplitude

A

Maximum displacement of an object from its equilibrium position

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5
Q

Define period

A

The time for one complete oscillation (one side to the other and back again)

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6
Q

Define frequency

A

Number of oscillations per unit time

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7
Q

Define angular frequency

A

The rate of change of angle in radians per second = 2pi x frequency

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8
Q

Define phase difference

A

The fraction of an oscillation between the vibrations of two oscillating systems expressed in radians or degrees

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9
Q

3 requirements for SHM

A
  1. Mass that oscillates 2. Equilibrium position 3. Restoring force that returns the mass to its equilibrium position
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10
Q

Explain why period of an object with SHM is independent of amplitude

A
  1. If you plot a graph of a=-(2pif)^2x it is a straight line with -ve gradient of (2pif)^2 through the origin 2. The gradient of the graph is independent of the amplitude 3. Therefore frequency also independent so the oscillator keeps steady time
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11
Q

Describe and draw the graph for the change of displacement in SHM

A

Sine curve starting at: a) (0,0) if beginning at equilibrium position b) (0,A) if starting at amplitude Max. displacement = amplitude

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12
Q

Describe and draw the graph for the change of velocity in SHM

A

-Velocity = rate of change of displacement -So graph = grad. of x/t graph -Phase diff. of 90 degrees w. x/t graph

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13
Q

Describe and draw the graph for the change of acceleration in SHM

A

-Acceleration is rate of change of velocity -So graph = gradient of v/t graph -a=-kx so it is also a reflection of x/t graph in x axis

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14
Q

Describe and explain the interchange between k.e. and p.e. in SHM

A

-Total energy is constant for an undamped system -k.e. max. at equilibrium position -p.e. max. at amplitude -Energy changes between k.e. and p.e.

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15
Q

Draw an energy/time graph for SHM

A

-Sine graph w. k.e. and p.e. -1 oscillation = 2 full waves on graph -Energy cannot be -ve

16
Q

Draw an energy/displacement graph

A

x-axis has -A to +A -Energy cannot be -ve

17
Q

Describe effects of damping on an oscillating system

A
  1. Oscillations lose energy due to friction 2. Amplitude of oscillations decreases exponentially 3. Frequency does not change (SHM) -@ start movement large so high air resistance and energy lost quickly -moving slower so less air resistance so energy lost less quickly
18
Q

Give an example of a forced oscillation

A
  1. Sitting on bus engines vibrations cause you to oscillate
19
Q

Describe and explain resonance using a graph

A

Amplitude/driving frequency graph 1. In resonance energy is transferred to the system most efficiently so absorbs greatest poss. energy 2. Natural f = f of driver 3. Amplitude is maximum

20
Q

Give 3 examples of useful resonance

A
  1. Microwaves: f of microwaves (driver) = natural f of water mols in food -> heats food as water absorbs energy 2. MRI: f of radio waves (driver) = natural f of hydrogen nuclei 3. Radio/TV aerial: tuner adjusted so natural f = f of chosen station (driver) so circuit produces large current for this f only
21
Q

Give 3 examples where resonance is harmful and solutions

A
  1. Car springs: vibrate when going over a bump -> damped by shock absorbers 2. Buildings: during earthquake forced to oscillate by vibrations of the earth (driver) -> shock absorbing foundations 3. Suspension bridges: wind causes resonance and damages bridge
22
Q

Give 3 examples of SHM

A
  1. Vibrating strings of a musical instrument 2. Alternating current electrons vibrate with SHM 3. Atoms in a molecule vibrate with SHM
23
Q

Describe acceleration in SHM

A
  1. Directly proportional (but opp. direction) to displacement from equilibrium position 2. Always directed towards equilibrium position
24
Q

In SHM what is the relationship between max v and A

A

Directly proportional: 1. SHM has T independent of A 2. If A increases, the object will have to travel a greater distance in the same amount of time so will have to move faster

25
Q

What’s the relationship between max v and frequency in SHM

A

Directly proportional 1. If the frequency increases T goes down 2. Therefore a given distance must be covered in a shorter time so speed increases

26
Q

What happens to energy when oscillations are damped

A
  1. Energy is removed from the system as heat by friction 2. A and max v decrease

Physics Unit 1 (4 decks)

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