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B1 M2 - Physics > 2.2 Mechanics - Kinetics (Lvl 2) > Flashcards

2.2 Mechanics - Kinetics (Lvl 2) Flashcards

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1
Q

What is motion?

A

A continuing change of position or the process in which a body undergoes displacement.

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2
Q

How could motion be described in an object?

A

When it is at different points in space at different times.

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3
Q

How would the motion be uniform?

A

When the distance the object moves remains the same for a given period of time.

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4
Q

What does a body change when its acceerates?

A

Speed or direction.

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5
Q

In linear motion, what changes when a body acclerates?

A

A change in speed.

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6
Q

Which type of acceleration remains constant?

A

Earth gravitational attraction.

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7
Q

What is the standard value for graviational accerlation?

A

9.8m/s^2.

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8
Q

What is uniform circular motion?

A

An object that is in motion in a circle at a constant speed, which is continually changing its direction.

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9
Q

What is the force required to keep an object moving in a curve path?

A

Centripetal force.

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10
Q

What is the formula for centripetal force?

A

centripetal force = mass x velocity^2/radius.

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11
Q

What is the meaning of centripetal accelration?

A

Because there is a constant change in direction, therefore a constant change in accerlation.

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12
Q

What is the meaing of centrifugal force?

A

The force that is equal to centripetal force, but in an opposite direction.

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13
Q

What always act at the same time on an object moving in a circular motion?

A

Centripetal and centrifugal force.

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14
Q

Which force keeps an object moving in a curved path directed towards the centre of rotation?

A

Centripetal force.

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15
Q

Which force keeps an object moving in a curved path directed way from the centre of rotaion?

A

Centrifugal force.

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16
Q

What does pendual motion describe?

A

The movement which the pendulum will undergo if it is given a small displacement from its vertial position and then allowed to swing freely under gravity.

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17
Q

What are the important terms associated with pendular motion? (6)

A
  1. Angular amplitude.
  2. Oscillation/vibration
  3. length of the pendulum
  4. periodic time
  5. cycle
  6. frequency.
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18
Q

What is angular ampltiude?

A

Angular displacement from rest to maxiumum swing position.

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19
Q

What is oscillation/vibration?

A

One complete swing to and from maximum position.

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20
Q

What is the length of pendulum?

A

Distance from the pivot point to the centre of gravity of the bob.

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21
Q

What is period time?

A

Time taken to complete one oscillation.

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22
Q

What is a cycle?

A

The motion completed in one period.

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23
Q

What is frequency?

A

Number of cycles completed in unit time.

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24
Q

What has been visible from experiments regarding a pendulum?

A

That provided the pendulum has a displacement of only a few degrees, that the periodic time remains constant even as the movement slows down.

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25
Q

What other variable makes no difference to period time of a pendulum?

A

The mass of the bob.

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26
Q

What variable changes the periodic time?

A

The length of the pendulum.

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27
Q

What can be said about the length of the pendulum?

A

The period of a pendulum increases with an increase in pendulum length or decrease in gravity.

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28
Q

What is damping?

A

Is a decrease of vibrations as a result of removing energy through resistance to motion.

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29
Q

Why is damping necessary in aircraft?

A

To control vibrations in order to prevent them from damaging aircraft components.

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30
Q

Why might vibrations be desirable?

A

Necessary for the function of the particular device.

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31
Q

How might vibrations be undesirable?

A

Imbalances from rotating parts.

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32
Q

What are the two types of vibration?

A
  1. Free vibration

2. forced vibration.

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33
Q

What is free vibration?

A

When a mechanical system is set off with an inital input and then allowed to vibrate freely.

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34
Q

What is forced vibration?

A

When a continuous force or motion is applied to a mechanical system.

35
Q

In forced vibration, what is the frequency of he vibration dependant on?

A

The force or motion applied.

36
Q

In forced vibration, what is the magnitude of the vibration strongly dependant on?

A

The behaviour of the mechanical system.

37
Q

What is resonance?

A

The tendancy of a system to oscillat at a maximum amplitude at a certain frequency.

38
Q

What form of vibration is useful in electrical circuits?

A

Resonance.

39
Q

What is velocity ratio?

A

The ratio of the distance moved by the point of application of the effort to the distance moved by the load in a simple machine.

40
Q

What is the formula for velocity ratio?

A

Velocity ratio = distance in/ distance out.

41
Q

What is mechanical advantage?

A

The ratio of the forced produced by a machine to the force applied to it.

42
Q

What is mechanical advantage used for?

A

Assessing the performance of the machine.

43
Q

What is the formula for mechanical advantage?

A

Mechanical advantage = resistance/effort.

44
Q

What is actual mechanical advantage?

A

The ratio of the output force and the input force.

45
Q

What does actual mechanical advantage tell us?

A

How much easier the work can be done.

46
Q

What is the formula for actual mechanical advantage?

A

actual mechanical advantage = output force/ input force.

47
Q

What is ideal mechanical advantage?

A

The mechanical advantage that would exist if there were no friction in the machine.

48
Q

What is the formula for ideal mechanical advantage?

A

ideal mechanical advantage = input distance / output distance.

49
Q

What is the simplest machine?

A

The lever.

50
Q

What are the three basic parts of a lever?

A
  1. the fulcrum
  2. force 1 or effort applied at a distance from the fulcrum.
  3. a load or resistance which acts at a distance from the fulcrum.
51
Q

What is a first class lever?

A

Where a fulcrum is between the effort and load applied to a rod.

52
Q

What is the formula for a first class lever?

A

f1 x s1 = f2 x s2

53
Q

What is a second class lever?

A

The fulcrum is at one end of the lever and the effort is at applied to the opposite end, with the resistance in between the two.

54
Q

What is the most common type of lever?

A

Third class lever.

55
Q

What is a third class lever?

A

The fulcrum at one end, with the effort in between the load/resitance and the fulcrum.

56
Q

What is an inclined plane?

A

A plane surface inclined to a horizontal plane at any angle other than a right angle.

57
Q

How does an inclined plane achieve an advantage?

A

By allowing a large resistance to be moved by a small effort over a long distance.

58
Q

How would you calculate the effort required for an inclined plane?

A

Using the same formula as first and second class levers.

F1 x s1 = F2 x s2.

59
Q

How are pulleys similar to levers?

A

Because the location of the pulley determines whether it is a 1st, 2nd or 3rd class lever.

60
Q

How would you determine the mechanical advantage of a pulley?

A

Count the number of ropes that move or support a moveable pulley.

61
Q

What happens when mechanical advantage is gained?

A

The distance on which effort is applied increases.

Ie, MA of 2, for every 1m the resistance moves, effort must be applied to 2m of rope.

62
Q

How is mechanical advantage gained through gears?

A

Variable number of teeth used on the drive or driven gear.

63
Q

How do you calculate the mechanical advantage of gears?

A

MA = driven gear/ drive gear.

64
Q

How do you calculate the force input when turning a gear?

A

= (gear ratio divided by each other) x force applied

65
Q

What is torque proportional to?

A

Horsepower.

66
Q

What is torque inversely proportional to?

A

Rotational speed (rpm).

67
Q

What is the formula for horsepower?

A

Hp= torque x rpm/ 5252.

68
Q

What does the constant 5252 represent?

A

Converting rpm to radians per second.

69
Q

What is the difference between revolution ratio and gear ratio?

A

Revolution ratio is opposite to gear ratio.

Gear ratio = 2:1
Revolution ratio = 1:2.

70
Q

What is a spur gear?

A

Teeth cut straight across their circumference and are used to connect two parallel shafts.

71
Q

Which direction does a spur gear rotate if both gears have external teeth?

A

In opposite directions to each other.

72
Q

Which direction does a spur gear turn if one of gears has internal teeth?

A

In the same direction as each other.

73
Q

What is a bevel gear?

A

Gear having teeth cut into a conical surface known as the pitch zone.

74
Q

When would a bevel gear be used?

A

When the drive and drive shafts are not parallel to each other.

75
Q

What direction do bevel gears rotate and why?

A

In opposite directions to each other because they have external teeth.

76
Q

At what angles can bevel gears be used?

A

Any angle below 180 degrees, but typically 90 degrees.

77
Q

What is a worm gear?

A

A toothed wheel worked by a short revolving cylinder called the worm, resembling a screw thread

78
Q

When would a worm gear be used?

A

When a large reduction in speed in needed and correspondingly high torque multiplication.

79
Q

What is a sun and planet gear?

A

A drive gear (sun), drives the driven gear (planets) around a fixed outer ring.

80
Q

Which direction is the output gear rotating in a sun and planet gear?

A

In same direction as the sun gear.

81
Q

When is the sun and planet gear often used?

A

When space and weight are an issue and when a large amount of speed reduction and torque is needed.

82
Q

What is efficiency?

A

The ratio of work which is transferred to a useful form compared to the total input work.

83
Q

Why can’t a machine be 100% efficient?

A

Because of losses such as heat, friction, deflection as well as wear and tear.

B1 M2 - Physics (9 decks)

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