Topic 3 - Oscillations Flashcards

1
Q

Oscillation

A

Continuously repeated movements

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2
Q

Period (T)

A

The time taken for an object to complete one full oscillation

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3
Q

Simple harmonic motion

A

The motion of an oscillating system.

There’s usually restoring force during the SHM, which tries to return the object to its Centre position

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4
Q

Restoring force

A

F = -kx
Where the force is proportional to the distance from the center position and k is a constant that depends on the particular oscillating system

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5
Q

Amplitude

A

The maximum displacement from the equilibrium position

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6
Q

Period of a pendulum

A

T = 2π√l/g

Where L is the length of the pendulum string

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7
Q

Angular velocity

A

• ω = θ/t
Where t is the time in seconds

• ω = 2πf

• ω = 2π/T
Where T is the period

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8
Q

Horizontal distance

A

x = r cosθ

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9
Q

Moving in a circle

A

x = r cos(ωt)

R can also be amplitude

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10
Q

ω of a pendulum is √g/L

L is the length of the string of the pendulum

A

ω of a string is √k/m

K is the restoring force constant

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11
Q

Acceleration acts in the opposite direction to the displacement

A

When displacement is zero so is the acceleration

And when X is max so is acc

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12
Q

The displacement graph is a cosine graph

A

The acceleration graph is a negative cosine graph

The velocity is a negative sine graph

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13
Q

During a swinging motion of a pendulum, at each end of the swing, it’s velocity is zero

A

So it has zero kinetic energy and a maximum potential energy at this point

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14
Q

When the bob passes through the central position, it’s velocity is at a maximum

A

And the kinetic energy is at a maximum while the potential energy is at a minimum

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15
Q

Free oscillation

A

A continuous exchange of PE and KE, caused by a restoring force which is proportional to the displacement.

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16
Q

Natural frequency

A

The frequency at which the oscillating system naturally oscillates without external forces

17
Q

Forced oscillation

A

Forcing the the oscillating system to oscillate at another frequency than its natural one.
The frequency is called driving frequency

18
Q

Damped oscillations

A

These suffer a loss of energy in each oscillation reducing the amplitude over time

19
Q

Types of damping:

A

Under damping

Over damping

Critically damped (overshooting)

20
Q

Under damping

A

It’s when the oscillator completed several oscillations and the amplitude decreases exponentially
E.G. A normal pendulum

21
Q

Overdamping

A

The amplitude of the oscillation may drop so rapidly that the oscillator does not even complete one cycle
E.g. under water

22
Q

Critical damping or overshooting

A

When the oscillator returns to its equilibrium position in the quickest possible time without going past that position

23
Q

Undamped oscillation

A

Is when no energy is lost during oscillations

24
Q

Resonance

A

Is when a system is forced to vibrate at its natural frequency, absorbing more and more energy and thus increasing the amplitude.

25
A simple setup of several pendulums can demonstrate resonance. They heavy swinging ball acts through the suspension wire to drive all the other pendulums at its natural frequency.
Only the pendulum with the same natural frequency will vibrate with a large amplitude. The pendulum has the same length of wire as the driving pendulum. The other pendulums show little movement because the driving frequency doesn't match their natural frequency
26
As the driving frequency applied to an oscillating system changes, it will pass through Natural frequencies of the system which causes large amplitude vibrations
The size of the vibrations at resonant frequencies can be so great that they damage the system