Physics Unit 4 - Circular motion & Oscillations.

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  • Created by: Phil
  • Created on: 11-04-13 14:51
Define unifrom circular motion.
The motion of an object in a circle with a constant uniform speed.
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How is the speed of an object in uniform circular motion found?
Speed = Cicumference of the orbit/ time taken for one orbit.... V=2πr/T
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Define angular frequency (ω) and what is it measured in?
ω = 2π/T or ω=2πf, where T is the period in seconds and f is frequency in Hertz.It is measured in radians per second.
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Define Centripetal force.
The term used for any force that allows an object to travel in a circle or part circle and acts along the radius towards the centre of the circle.
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Equation for centripetal force?
F = mv^2/r
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Centripetal acceleration?
a = V^2/r
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In a gravitational field diagram, what does the positioning of the arrows tell us?
If the arrows are far apart the force is weak, close together strong, evenly spaced uniform.
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Define field strength (with the equation).
Field strength = Force per unit mass. g = F/m
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The radial field produced by mass M at a distance r from M is given by ...
g= -GM/r^2
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How is the force between two objects found?
F= -Gm1m2/ r^2, where m are the masses in kg and r is the distance between them.
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Newton's law of gravitation (words)
any two bodies that attract each other with a force that is proportional to each of the masses and inversely proportional to the square of the distance between them.
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Inverse square law.
If an object is 2xr away, then 1/4 of the force is given.
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Define weightlessness.
A body that experiences no gravitational field i,e there would be zero field.
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2 Features of geostationary satellites.
1. Have an orbital period of 24hrs 2. always appear to be above one point on the equator.
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What are geostationary satellites used for?
Mostly for communications. for eg satellite tv where the satellite receiver dish is always pointed in the direction of the geostationary satellite.
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What does Kepler's third law show?
T^2 proportional to R^3 for a body of mass m orbiting a central mass M at distance R.
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How is Kepler's third law found?
GMm/ r^2 = mV^2/ r , V= 2πr/ T, substituting V in and canceling and rearranging gives .. T^2 = 4π^2/GM R^3.
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In terms of oscillations, define frequency.
The number of complete oscilations performed per seond.
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In terms of oscillations, define angular fequency.
Measures rotation rates in rads^-1
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In terms of osillations, define peropd.
The time taken to perform one complete cycle of oscillation.
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In terms of osscillations, define amplitude.
The max displacemant that the particles obtain from their central undisturbed position.
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In term of oscilattions define displacement,
How far each particle is from it's central undisturbed position.
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In terms of oscilaations define phase difference.
The phase angle by which one wave leads or lags another.
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Define simple harmonic motion.
A body moves with SHM if it's acceleration is directed towards the equilibrium and it's acceleration is proportional to it's dispalcement.
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Equation for SHM?
a = -(2πf)^2 x, where a= accel, f= freq of oscillation, x= displacement.
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Define free oscillations.
Occur when a system is given a initial disturbance, then left to virbate without any resistance forces. The system vibrates at nat freq
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Define damping.
Resistive forces that are present, reduce the amplitude of oscillations. This process is damping.
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Forced oscillations.
Occur when a system is subjected to a periodic force. Frequency of the vibrations is the freq of the applied force.
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Energy change during SHM.
When a mass passes through it's equib position, v and therefore ke is at a max. At max displacement, v and therefore ke are at a minimum and Pe is a at a max.
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What is to be assumed during energy change of SHM.
No friction or air drag, meaning total energy will remain constant.
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Define light damping.
Exponential decrease in amplitude over several oscillations.
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Define Very heavy damping.
No oscillations at all.
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Define critical damping.
Occurs when mass returns to rest in the shortest possible time without over shooting.
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When does resonane occur and what does it result in ?
Occurs when a periodic force is applied to a system that matches the natural frequency of te system. It results in maximum amplitudes.
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Useful example of resoance?
Microwave cooking,, frequency applied matches the nat frequency of the water molecules, causing them to vibrate more.
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Destructive ecample of resonance?
Earthquakes, if the frequency applied by the eq, matches the nat frequency of a structure, then this results in the maximum damage to the structure.
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Other cards in this set

Card 2

Front

How is the speed of an object in uniform circular motion found?

Back

Speed = Cicumference of the orbit/ time taken for one orbit.... V=2πr/T

Card 3

Front

Define angular frequency (ω) and what is it measured in?

Back

Preview of the front of card 3

Card 4

Front

Define Centripetal force.

Back

Preview of the front of card 4

Card 5

Front

Equation for centripetal force?

Back

Preview of the front of card 5
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