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ALevel Physics NEW > Section 6 part 2 - Further mechanics and thermal physics (circular and sh motion) > Flashcards

Section 6 part 2 - Further mechanics and thermal physics (circular and sh motion) Flashcards

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1
Q

Define uniform circular motion

A

An object rotating at a steady speed

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2
Q

Why do you accelerate when moving at a constant speed around a circle?

A

Velocity is continually changing due to change in direction. If velocity changes, there must be an acceleration as acceleration is rate of change of velocity

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3
Q

Which direction does the velocity act on an object in uniform circular motion?

A

Along the tangent to the circle at that point

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4
Q

Which direction does the centripetal force act on an object in uniform circular motion?

A

Towards the centre

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5
Q

Why does the acceleration of an object in uniform circular motion act towards the centre of the circle?

A

Because the change in direction of the velocity is towards the centre of the circle, so the acceleration acts towards the centre of the circle

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6
Q

What causes an object to move around on a circular path?

A

Being acted upon by a resultant force

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7
Q

What is a centripetal force?

A

The resultant force causing an object to move around a circle at constant speed

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8
Q

What is the centripetal force acting on a car when going around a roundabout?

A

The sideways friction between the vehicle’s tyres and the road surface

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9
Q

State the difference in friction for a car going around a banked track vs non banked track

A

Banked track has no sideways friction

Non-banked track has sideways friction

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10
Q

Why do banked tracks not have sideways friction for a vehicle going around it?

A

Centripetal force is given by the support forces of the tyre

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11
Q

How can you get a velocity time graph from a displacement time graph?

A

Differentiate the graph

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12
Q

How can you get an acceleration time graph from a velocity time graph?

A

Differentiate the graph

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13
Q

Define SHM

A

A type of periodic motion where the acceleration is directly proportional to the displacement and acts in the opposite direction to that of the displacement

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14
Q

For a mass spring system oscillating vertically, if you have A at the peak. B at equilibrium and C at the bottom, describe the acceleration and velocity

A

A - Max acceleration down, 0 velocity
B - 0 acceleration, max velocity
C - max acceleration up, 0 velocity

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15
Q

What is the amplitude of an oscillating object?

A

The maximum displacement of the oscillating object from equilibrium

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16
Q

What do you call the oscillations if the amplitude is constant?

A

Free vibrations

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17
Q

What is the time period

A

Time taken for one complete cycle of oscillation

18
Q

What is the frequency

A

Number of cycles that pass a point per second

19
Q

What can you conclude when comparing the acceleration time graph against the displacement time graph?

A

Acceleration is always in the opposite direction to the displacement

20
Q

Which direction does the resultant force act on an oscillating object?

A

Towards equilibrium

21
Q

What is the restoring force?

A

The resultant force that acts towards equilibrium

22
Q

What determines the frequency of oscillation of a loaded spring?

A

Adding extra mass -> increases inertia which means each cycle of oscillation takes longer
Using weaker springs -> Restoring force would be less, acceleration would be less, each cycle of oscillation takes longer

23
Q

What is the restoring force for a spring oscillating vertically that obeys Hooke’s law?

A

-kx

24
Q

What is another equation for acceleration?

A

-kx/m

25
Q

How does the tension in the spring vary?

A

Max when stretched downwards (maximum displacement downwards) = mg + kA
Min when compressed upwards (maximum displacement upwards) = mg - kA

26
Q

What are free oscillations?

A

When an object oscillates with a constant amplitude because there is no friction acting on it

27
Q

What is the equation for SHM energy stored in a spring?

A

1/2kx^2

28
Q

What is the equation for SHM the total energy of the system?

A

1/2kA^2

29
Q

What is the equation for SHM kinetic energy

A

1/2k(A^2-x^2)

30
Q

What are dissipative forces?

A

Forces causing the amplitude to decrease by dissipating energy of the system to the surroundings as thermal energy

31
Q

When is a motion of an object said to be damped?

A

When dissipative forces are present

32
Q

When does light damping occur?

A

When the time period is independent of the amplitude so each cycle takes the same length of time as the oscillations die away

33
Q

What is critical damping?

A

When the oscillation returns to equilibrium in the shortest possible time without overshooting

34
Q

What is heavy damping?

A

When the object returns to equilibrium much more slowly than critical damping. No oscillating motion occurs e.g mass spring system in thick oil

35
Q

Describe the 3 types of damping on a displacement time graph

A

Light - Same time period, but amplitude gradually decreases
Critical - Quater of a cos wave
Heavy - Negative gradient graph
ALL START FROM SAME MAX DISPLACEMENT

36
Q

What is a periodic force?

A

A force applied at regular intervals

37
Q

What are forced vibrations?

A

A system undergoes forced vibrations when a periodic force is applied to it

38
Q

When does a system oscillate at maximum amplitude

A

When the phase difference between displacement and periodic force is 1/2 pi

39
Q

When does a system resonate?

A

When the periodic force is exactly in phase with the velocity of the oscillating system

40
Q

What is the frequency at maximum amplitude called?

A

Resonant frequency

41
Q

What happens to the resonance of a system when the damping is lighter?

A

The maximum amplitude becomes larger at resonance

the closer the resonant frequency is to the natural frequency of the system

42
Q

What is true for a an oscillating system with little or no damping at resonance in terms of frequencies?

A

Applied frequency of periodic force = natural frequency of system

ALevel Physics NEW (12 decks)

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