Further Mechanics and Thermal Physics (1): Motion in a Circle Flashcards

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1
Q

What unit is used for angles in SHM and circular motion?

A

radians

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2
Q

An object rotating at a steady speed is said to be in…?

A

Uniform circular motion

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3
Q

What is the equation for the linear speed of an object in uniform circular motion?

A

v = 2(pi)r/T

OR

v = 2(pi)rf

where:
2(pi)r - the circumference of the circle
T - the time taken for the object to complete one full rotation
f - frequency of rotation = 1/T

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4
Q

For a cyclist travelling at speed x, what is the speed of the perimeter of each wheel?

A

x ms^-1

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5
Q

What is the equation for angular displacement per second?

A

2(pi)/T

where:
T - the time taken for the object to complete oen full rotation

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6
Q

What is the equation for the angular displacement, theta, of an object in time t?

A

theta = 2(pi)t/T

OR

theta = 2(pi)ft

where:
theta - angular displacement
2(pi)/T - the angular displacement per second

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7
Q

What is the definition of angular displacement?

A

The radians swept by an object per second

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8
Q

What is the definition of angular speed, omega (lowercase)?

A

The angular displacement per second

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9
Q

What is the equation for angular speed?

A

omega = theta/t = 2(pi)t/T/t = 2(pi)/T

OR

2(pi)f

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10
Q

What is the unit of angular speed?

A

rads^-1

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11
Q

How do you convert from x radians to degrees?

A

180/(pi) multiplied by x radians = degrees

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12
Q

How do you convert from y degrees to radians?

A

(pi)/180 multiplied by y degrees = radians

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13
Q

What is the equation for the linear distance, s travelled by a particle in uniform circular motion in time, t?

A

s = vt = 2(pi)rt/T = (theta)r

theta = angular displacement in time t = 2(pi)t/T

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14
Q

What is the equation for the linear velocity for a particle in circular motion?

A

v = 2(pi)r/T = (omega)r

omega = angular speed = 2(pi)/T

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15
Q

Describe why objects in circular motion experience a constant force?

A
  • Objects moving in a circular path are constantly changing direction but moving at a constant speed
  • therefore, they have a constantly changing velocity and due to Newtons 1st law an object with a changing velocity is acted upon by a resultant force

OR

  • therefore, the object is accelerating and due to Newtons 2nd Law, F = ma, an object that is accelerating must be acted on by a resultant force in the direction of the acceleration
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16
Q

What direction does centripetal acceleration act for an object in circular motion?

A

Towards the centre of the circle

17
Q

What direction does centripetal force act for an object in circular motion?

A

Towards the centre of the circle

18
Q

What is acceleration?

A

The change in velocity per second/ the rate of change of velocity

19
Q

What direction does the velocity act for an object in uniform circular motion?

A

Tangent to the circle

20
Q

How does the velocity of an object in uniform circular motion change as it moves around the circle?

A

The change in direction of the velocity is towards the centre of the circle

21
Q

What is the name for the type of acceleration in uniform circular motion?

A

Centripetal acceleration

22
Q

What is the equation for centripetal acceleration (linear speed)?

A

a = v^2/r

23
Q

What is the equation for centripetal acceleration (angular speed)?

A

a = (omega)^2r

24
Q

What is the name for the type of force in uniform circular motion?

A

centripetal force

25
Q

What provides the centripetal force for an object being whirled around on the end of a string?

A

Tension in the string

26
Q

What provides the centripetal force for an object in a circular orbit?

A

The force of gravity between the object and the massive planet

27
Q

What is the equation for centripetal force of an object moving with uniform circular motion? (linear speed)

A

F = mv^2/r

as F = ma

28
Q

What is the equation for centripetal force of an object moving with uniform circular motion? (angular speed)

A

F = m(omega)^2r

29
Q

What is the equation for a the centripetal force of a car travelling over the top of a curved hill?

A

mg - S = mv^2/r

where:
S - The support force from the ground onto the car
mg - The weight of the car

30
Q

What happens to the support force, S, on a car when th vehicle exceeds a certain speed and loses contact with the road over a curved hill?

A

S = 0N

31
Q

What is the maximum v^2/r can equal for a car to remain on the ground when going over a curved hill?

A

v^2/r < 9.81

32
Q

What is the centripetal force when a car is going round a roundabout?

A

The sideways force between the tyres and the road surface

33
Q

What is the maximum frictional force of a material dependant on?

A

Its coefficient of friction

34
Q

If the speed of a car moving around a roundabout is too high, what happens?

A

The car slips/skids