Physics - Oscillations
OCR A-Level Physics 2022
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Flashcards
Onset and the circular motion link
What causes an object in an equilibrium position to start oscillating?
A force is applied that moves it from the equilibrium position.
How are circular motion and oscillations linked?
Measuring the displacement along the $x$-axis of an object moving in a circle forms an oscillating wave.
Acceleration in SHM
What is the formula for acceleration in simple harmonic motion?
What is always true about the direction of displacement and direction of acceleration in simple harmonic motion?
They are opposites.
What is always true about simple harmonic motion?
The acceleration is directly proportional to the displacement.
SHM equations of motion
What is the formula for the maximum amplitude in simple harmonic motion (SHM)?
What is the formula for the velocity in simple harmonic motion in terms of displacement $x$ and amplitude $A$?
What is the formula for the maximum velocity in simple harmonic motion?
What is the formula for the displacement $x$ for simple harmonic motion at time $t$ if you begin timing when the displacement is at the maximum?
What is the formula for the displacement $x$ for simple harmonic motion at time $t$ if you begin timing at the equilibrium position?
What is the definition of simple harmonic motion?
Motion where the acceleration is directly proportional to the displacement and is directed towards the equilibrium position.
SHM graphs
What is the graph of displacement against time, assuming you start measuring at the equilibrium position?
Calculator units in oscillation questions
When doing an oscillations question ($A\cos(\omega t)$, $A\sin(\omega t)$), what units should your calculator be in?
Radians!!
Why does your calculator have to be in radians for oscillation questions?
Because the angular frequency $\omega$ is in radians.
Distance and work over an oscillation
If the amplitude of an oscillator is $0.25m$, how far does it move in one complete oscillation?
If an oscillator has to overcome a mean dampening force of $0.25N$ for every $1m$ it moves per complete oscillation, what would be the formula for the energy expenditure per oscillation?
Energy in an oscillator
What does this show?
What does this show?How the energy of an oscillator changes (assuming you start measuring at the max).
What is the POTENTIAL energy of an oscillator at the EQUILIBRIUM position?
What is the KINETIC energy of an oscillator at the EQUILIBRIUM position?
The max.
What is always true about the total energy in an oscillator?
It remains constant.
Damping
How does light damping affect the amplitude of an oscillator?
It gradually reduces it.
How does light damping affect the period of an oscillator?
It remains the almost the same.
How does heavy damping affect the amplitude of an oscillator?
It quickly reduces it.
How does heavy damping affect the period of an oscillator?
It gradually reduces it.
How does very heavy damping affect the amplitude of an oscillator?
It reduces it to $0$ and remains at the equilibrium position.
How does very heavy damping affect the period of an oscillator?
It stops being an oscillator.
Free and forced oscillations
What is a free oscillation?
Oscillatory motion with no external forces applied.
What is a forced oscillation?
Oscillatory motion when an external driver force is applied.
What is the frequency of a forced oscillation?
The frequency of the driving force.
What is true about measuring the amplitude at period-length intervals if the oscillator is experiencing exponential damping?
There will be a constant ratio.
Resonance
When does resonance occur?
When the driving frequency is the same as the natural frequency.
What happens when resonance occurs?
The amplitude of the oscillator will increase dramatically.
How can an opera singer break a wine glass?
They sing at the natural, resonant frequency of the glass.
Amplitude independence of period
What is true about amplitude and period in SHM?
They are independent of one another.
What happens to the period of a pendulum if you raise the swinging bit further up (i.e. increase the amplitude)?
It remains the same.