AQA A2 Physics - What Goes Around Comes Around

Notes for 'what goes around comes around' for those studying AQA A2 Physics B: Physics in Context for the unit 4 exam, part of  a complete set of notes on here.

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  • Created on: 27-04-11 22:26
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What Goes Around Comes Around
Pendulums move repeatedly in one direction and then in the opposite
Passing through its rest position (also known as equilibrium position)
Displacement of the object from this equilibrium position continually changes with
time during the motion, following the shape of a sine or cosine graph
Quantities that help describe the motion
Amplitude (A)
Maximum displacement from the equilibrium position
Time Period (T)
Time take to complete once cycle of the oscillation
Frequency (f)
Number of cycles per second made by the object
Displacement, Velocity and Acceleration
Graphs can be drawn of all of these against time
Graphs are connected by their gradients and area under the curves
gradient = y -axis
area = x - axis ×y - axis
Simple Harmonic Motion (SHM):
Defined as the oscillatory motion in which the acceleration is always
o Proportional to the displacement from the equilibrium point
o In the opposite direction to the displacement (towards the equilibrium)
Can be written as
a =- (2f )2x
x = displacement
f = frequency
a = acceleration
Acceleration is always directed towards the equilibrium position, (hence the minus sign) and
acceleration is proportional to a constant x displacement, ie. acceleration displacement

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Solving SHM equation
x = Acos(2f t)
To solve needs to find a series of values of x which fit the equation.…read more

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T = 2 m
This can also be easily turned into the equation for frequency due to the link between them:
1 k
f = 2 m
Damping and Resonance:
Damping originates due to frictional forces and always opposes the motion of an object
The presence of constant damping does not alter the time period or frequency, it
only reduces the amplitude
Light damping
o Energy is lost slowly
o Oscillations stop slower
Heavy damping
o Energy is lost quicker
o Oscillations stop…read more

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For an undamped or lightly damped system there must be a periodic force applied at
the same natural frequency as that of the object
o Damping must dissipate less energy than the applied force provides the object with
For an object to resonate mechanical or electrical energy must build up in
the object. Anything which removes energy restricts the resonance
When the frequency of the applied force matches the natural frequency of an object
resonance occurs.…read more


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