Circular Motion Flashcards

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1
Q

Angular displacement

A

The angle through which an object moves in a given time

Measured in radians

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2
Q

Angular displacement formula

A

s=rθ

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3
Q

Angular displacement for a full circle

A

2π radians

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4
Q

Radians to degrees and vice versa

A

Shift
Set up
2

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5
Q

Linear velocity

A

Rate of change of linear displacement

Measured in meters/second

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6
Q

For an object in circular motion, its linear velocity is what

A

Tangential to the objects circular path

Constantly changing as the object moves around in a circle

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7
Q

Angular velocity equation

A

w=△θ/△t

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8
Q

Angular velocity

A

Rate of change of angular displacement

Measured in radians/second

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9
Q

rpm

A

Revs per minute
How many revolutions completed in a minute
rms(revs^-1)=Frequency=rpm/60

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10
Q

revs^-1 into rads^-1

A

x2π

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11
Q

Angular velocity given frequency

A

2πf

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12
Q

Angular velocity given time period

A

2π/T

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13
Q

Linear velocity given frequency

A

2πrf

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14
Q

Linear velocity given time period

A

2πr/T

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15
Q

Frequency

A

Number of complete revolutions per second

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16
Q

Is a ball swung around someone’s head accelerating if traveling at a constant speed in a circle

A

Yes
Speed is constant
But velocity is constantly changing since constantly changing direction
Acceleration = Change in velocity/time

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17
Q

What must act on a ball to keep it moving in a circular path when swung around a head

A

A resultant force
Centripetal force
Always acting towards the centre of rotation
Coming from the tension

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18
Q

What happens if the string swinging a ball in a circle snaps

A

No longer accelerates towards the centre
Continues moving at the same speed in the same direction as when the string snapped
Travels in a parabolic path in free fall from the side perspective (acceleration acting vertically down)
From above follows a tangential path, following Newton’s first law

19
Q

Centripetal acceleration

A

Acts towards the centre of rotation and keeps objects in circular motion along with the centripetal force

20
Q

What are the centripetal force and centripetal acceleration always perpendicular to

A

(linear) Velocity

21
Q

What happens if the centripetal force increases

A

Either remains the same distance from the centre but at an increased velocity
Or moves closer to the centre and remains at the same velocity

22
Q

What happens if the centripetal acceleration decreases

A

Either remains at the same distance from the centre but travels with a smaller velocity
Or moves further from the centre and continues with the same velocity

23
Q

Centripetal acceleration for linear velocities

A

v^2/r

24
Q

Centripetal acceleration for angular velocities

A

w^2r

25
Q

Examples of centripetal forces

A
Gravitational attraction
Friction
Magnetic force
Reaction and weight
Tension
Lift and weight
26
Q

What forces contribute to the centripetal force

A

Any components of forces acting towards the centre of rotation

27
Q

Centripetal force greater than maximum

A

Circular motion does not happen
Force is too weak to maintain circular motion
String breaks, car skids off roundabout

28
Q

Centripetal less than or equal to maximum

A

Circular motion happens

29
Q

What happens if a car enters a bend at a speed higher than the maximum speed

A

Centripetal force is greater than the maximum friction
Car will skid off and move to a greater radius
Circular motion couldn’t be maintained at that radius

30
Q

Other phrases for reaction

A

Normal contact

Support force

31
Q

What must be taken into account in vertical circular motion

A

Force acting readily (tension, reaction)

Weight (vertical component)

32
Q

Increasing speed for non fixed radius

A

Centripetal force the same

Radius increases

33
Q

Increasing speed for fixed radius

A

Centripetal force increases

34
Q

Decreasing speed for non fixed radius

A

Centripetal force the same

Radius decreases

35
Q

Decreasing speed for fixed radius

A

Centripetal force decreases

36
Q

Centripetal force equation on the underside of the top of a loop in circular motion

A

Fcentri=W+R

37
Q

Centripetal force equation on top of a loop in circular motion

A

Fcentri=W-R

38
Q

Centripetal force equation on the bottom of a loop in circular motion

A

Fcentri=R-W

39
Q

For a ball on a string in vertical circular motion where is tension maximum and why

A

Bottom
Fcentri=T-W
For Centripetal force to remain constant, the tension must be greatest here since weight is constant

40
Q

For a ball on a string in vertical circular motion where is tension minimum and why

A

Top
Fcentri=T+W
For Centripetal force to remain constant, the tension must be smallest here since weight is constant

41
Q

Does the highest speed a car can travel over the hill change for a car with greater mass

A

No
Stays the same since v max = root (gr)
g is constant and so is r so vmax stays the same
Mass is not included in the equation/vmax independant of mass

mv^2/r=mg
m will cancel because although two different masses being compared when working out the vmax its the mass of the same object

42
Q

For a conical pendulum, what is the effect of increasing the velocity

A

Tension in the vertical direction must stay the same as it must be equal to the weight since in vertical equilibrium
Fcentri will increase since the tension in the horizontal direction will increase
So radius must increase
Meaning that the angle to the vertical will be greater

43
Q

Why will a ball being swung in horizontal motion never be perfectly horizontal

A

The weight of the wall acts vertically down
In order for it to be in vertical equilibrium there must be a vertical component of tension of the centripetal force
Meaning that it will always be angled by some amount