5.2 Circular Motion And Oscillations

Question 1

How many radians are there is 360 degrees?

Answer 1

2 pi

Question 2

What are the SI units of angular velocity?

Answer 2

Radians per second

Question 3

What is the definition of angular velocity?

Answer 3

The rate of change of angle.

Question 4

How do you calculate angular velocity from time period (T)?

Answer 4

Angular velocity = 2 pi / T

Question 5

How do you calculate angular velocity from frequency (f)?

Answer 5

Angular velocity = 2 pi f

Question 6

What is required for uniform circular motion?

Answer 6

A constant net force that always acts perpendicular to velocity.

Question 7

Why doesn’t a centripetal force do any work on an object in circular motion?

Answer 7

The force has no component in the direction of motion/is always perpendicular to motion.

Question 8

How do you calculate linear velocity from the time period (T) of an object in circular motion?

Answer 8

v = 2 pi r / T

Question 9

How do you calculate linear velocity from angular velocity?

Answer 9

v = angular velocity x radius

Question 10

How is it possible for an object to experience an acceleration but travel at a constant speed?

Answer 10

If acceleration is perpendicular to velocity, the velocity will change direction whilst speed is constant.

Question 11

What provides the centripetal force for a car turning a corner?

Answer 11

Friction from the road on the tyres.

Question 12

What provides the centripetal force on the moon?

Answer 12

The gravitational attraction of the Earth.

Question 13

Apart from friction what contributes to the centripetal force on a banked track?

Answer 13

The horizontal component of the normal reaction.

Question 14

If a mass on a string is swung in a vertical circle where is the tension greatest?

Answer 14

At the bottom of the circle

Question 15

If a mass on a string is swung in a vertical circle where is the tension least?

Answer 15

At the top of the circle.

Question 16

Experiment for circular motion

Answer 16

dont forget

Question 17

What is the equilibrium position in an oscillation?

Answer 17

The point at which an object experiences no resultant force and thus no acceleration (the ‘rest’ position of an object).

Question 18

What are the conditions required for SHM?

Answer 18

The acceleration of an object is proportional, to its displacement from equilibrium and always in the opposite direction.

Question 19

What is the acceleration of an object undergoing SHM when it’s displacement is zero?

Answer 19

Zero

Question 20

What is an Isochronous oscillator?

Answer 20

An oscillator with a period/frequency that is not dependent on amplitude. (Always simple harmonic oscillators)

Question 21

What is a fiducial marker?

Answer 21

A pin or pointer placed at the equilibrium position of an oscillation.

Question 22

What measures can be taken to improve the accuracy when measuring the time period of SHM?

Answer 22

Time over multiple oscillations and calculate the average of several repeats.

Question 23

What is the kinetic energy of an SHM oscillator at maximum displacement?

Answer 23

Zero

Question 24

How does the total energy in an SHM oscillator vary with time?

Answer 24

It is constant.

Question 25

At what displacement is the potential energy of an SHM oscillator at a maximum?

Answer 25

At maximum displacement (x=±A).

Question 26

Define angular frequency

Answer 26

Product of 2 pi f

Question 27

Define phase difference

Answer 27

overall change in position from equilibrium point

Question 28

What is free oscillation?

Answer 28

No transfer of energy to and from the surroundings

Question 29

What is forced oscillations?

Answer 29

Happens when there is an external driving force, the frequency of this force is called the driving frequency

Question 30

What is the effect of damping on an oscillatory system?

Answer 30

Reduces the amplitude of the oscillation over time.

Question 31

What is critical damping?

Answer 31

Reduces the amplitude in the shortest possible time

Question 32

Give an example of a critically damped system

Answer 32

Car suspension | Moving coil meter (controls the arm in analogue voltmeters and ammeters

Question 33

What is overdamping, and what is the graph (xt) like?

Answer 33

They take longer to return to equilibrium than a critically damped system

Question 34

How is plastic deformation linked to damping?

Answer 34

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.

Question 35

Describe a lightly damped system and its effect on resonance

Answer 35

They have a sharp resonance peak. Their amplitude only increases dramatically when the driving frequency is very close to the natural frequency.

Question 36

Describe a heavily damped system and its effect on resonance

Answer 36

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

Question 37

Are loudspeakers heavy or lightly damped?

Answer 37

Heavy damped, so avoids being damaged by resonance.

Question 38

When does damping happen?

Answer 38

When energy is lost to surroundings, usually due to frictional force

Question 39

How do you investigate how amplitude varies with driving frequency? How can you adapt it to investigate damping?

Answer 39

- 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.

Question 40

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)

Answer 40

* 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.