5.2 Circular Motion And Oscillations Flashcards
How many radians are there is 360 degrees?
2 pi
What are the SI units of angular velocity?
Radians per second
What is the definition of angular velocity?
The rate of change of angle.
How do you calculate angular velocity from time period (T)?
Angular velocity = 2 pi / T
How do you calculate angular velocity from frequency (f)?
Angular velocity = 2 pi f
What is required for uniform circular motion?
A constant net force that always acts perpendicular to velocity.
Why doesn’t a centripetal force do any work on an object in circular motion?
The force has no component in the direction of motion/is always perpendicular to motion.
How do you calculate linear velocity from the time period (T) of an object in circular motion?
v = 2 pi r / T
How do you calculate linear velocity from angular velocity?
v = angular velocity x radius
How is it possible for an object to experience an acceleration but travel at a constant speed?
If acceleration is perpendicular to velocity, the velocity will change direction whilst speed is constant.
What provides the centripetal force for a car turning a corner?
Friction from the road on the tyres.
What provides the centripetal force on the moon?
The gravitational attraction of the Earth.
Apart from friction what contributes to the centripetal force on a banked track?
The horizontal component of the normal reaction.
If a mass on a string is swung in a vertical circle where is the tension greatest?
At the bottom of the circle
If a mass on a string is swung in a vertical circle where is the tension least?
At the top of the circle.
Experiment for circular motion
dont forget
What is the equilibrium position in an oscillation?
The point at which an object experiences no resultant force and thus no acceleration (the ‘rest’ position of an object).
What are the conditions required for SHM?
The acceleration of an object is proportional, to its displacement from equilibrium and always in the opposite direction.
What is the acceleration of an object undergoing SHM when it’s displacement is zero?
Zero
What is an Isochronous oscillator?
An oscillator with a period/frequency that is not dependent on amplitude. (Always simple harmonic oscillators)
What is a fiducial marker?
A pin or pointer placed at the equilibrium position of an oscillation.
What measures can be taken to improve the accuracy when measuring the time period of SHM?
Time over multiple oscillations and calculate the average of several repeats.
What is the kinetic energy of an SHM oscillator at maximum displacement?
Zero
How does the total energy in an SHM oscillator vary with time?
It is constant.
At what displacement is the potential energy of an SHM oscillator at a maximum?
At maximum displacement (x=±A).
Define angular frequency
Product of 2 pi f
Define phase difference
overall change in position from equilibrium point
What is free oscillation?
No transfer of energy to and from the surroundings
What is forced oscillations?
Happens when there is an external driving force, the frequency of this force is called the driving frequency
What is the effect of damping on an oscillatory system?
Reduces the amplitude of the oscillation over time.
What is critical damping?
Reduces the amplitude in the shortest possible time
Give an example of a critically damped system
Car suspension
Moving coil meter (controls the arm in analogue voltmeters and ammeters
What is overdamping, and what is the graph (xt) like?
They take longer to return to equilibrium than a critically damped system
How is plastic deformation linked to damping?
Plastic deformation of ductile materials reduce the amplitude of oscillations in the same way as damping.
As the material changes shape, energy is absorbed so smaller oscillations.
Describe a lightly damped system and its effect on resonance
They have a sharp resonance peak.
Their amplitude only increases dramatically when the driving frequency is very close to the natural frequency.
Describe a heavily damped system and its effect on resonance
Heavily damped systems have a flatter response.
Their amplitude doesn’t increase very much near the natural frequency and they aren’t as sensitive to the driving frequency
Are loudspeakers heavy or lightly damped?
Heavy damped, so avoids being damaged by resonance.
When does damping happen?
When energy is lost to surroundings, usually due to frictional force
How do you investigate how amplitude varies with driving frequency? How can you adapt it to investigate damping?
- Have a mass oscillating with large amplitude at resonant frequency on vertical springs
- Attach to vibration generator attached to signal generator
- Vary driving frequency
To investigate damping add disc to mask to increase air resistance.
Plan how you can obtain experimentally the displacement against time graph for the oscillating mass in the laboratory.
Include any steps taken to ensure the graph is an accurate representation of the motion
(4 marks)
- Motion sensor connected to data logger which sends information on displacement and time to computer.
- Sensor placed close to moving mass to eliminate reflections from other objects.
- Small reflector attached to mass
Any attached reflector should not cause damping.
• Motion sensor directed along line of oscillation or motion sensor signal blocked by supports so must be as near to line of oscillation as possible.
• Use thin supports to reduce reflections.
