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Cat B- Mod 2 Physics > 2.2.2 Mechanics- Kinetics > Flashcards

2.2.2 Mechanics- Kinetics Flashcards

1
Q

What is speed?

A

Constant forward movement without acceleration (constant velocity).

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2
Q

What is the equation for acceleration?

A

V²-U² divided by 2x distance

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3
Q

In what situation does acceleration remain constant?

A

When caused by earths gravitational attraction.

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4
Q

What is gravities standard value?

A

9.8m/s²

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5
Q

What is uniform circular motion?

A

Motion of an object in a circle at a constant speed, continually changing direction.

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6
Q

What is uniform circular motion also known as?

A

Centrifugal/Centripetal

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7
Q

What is centripetal force?

A

The force needed to keep an object moving in a circular motion and is facing in towards the centre.

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8
Q

What is the difference between centripetal and centrifugal?

A

Centripetal pulls the object in like gravity, centrifugal wants to push it away.

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9
Q

What is pendular motion?

A

The movement of a pendulum when it is given a small displacement and allowed to swing under gravity.

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10
Q

In pendular motion what is the angular amplitude?

A

Angular displacement from rest to maximum swing position.

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11
Q

In pendular motion what is the oscillation?

A

One complete swing

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12
Q

In pendular motion what is the length of the pendulum?

A

Distance from pivot to bob.

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13
Q

In pendular motion what is the frequency?

A

Number of cycles completed in unit time.

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14
Q

Does the mass of the bob make a difference to periodic time?

A

No

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15
Q

In pendular motion what is the periodic time?

A

Time taken to complete one oscillation.

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16
Q

What changes the periodic time of a pendulum?

A

The length of the pendulum.

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17
Q

What is damping?

A

Decrease of oscillations as a result of removing energy through resistance to motion.

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18
Q

What is free vibration?

A

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

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19
Q

What is forced vibration?

A

When a continuous force is applied to a mechanical system.

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20
Q

What is a harmonic?

A

Periodic vibration. Sinusoidal with constant amplitude.

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21
Q

What are the two waves in a harmony?

A

The harmonic and the fundamental frquency?

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22
Q

What is resonance?

A

The tendency of system to oscillate at a max amplitude at a certain frequency.

23
Q

What is the equation for wavelength of a harmonic?

A

2 divided by index of harmonic x length of the body

24
Q

What is the equation for resonance frequency?

A

1 divided by 2π x square root of gravity divided by length.

25
Q

What happens if a aircraft component vibrates at its resonant frequency?

A

The oscillations will become really large and the component could be destroyed.

26
Q

What do machines do?

A

Let us do more work easily but not reduce the amount of work.

27
Q

What is the velocity ratio?

A

The ratio of the distance moved by the point of application of the effort.

28
Q

What does it mean if the velocity ratio is greater than one?

A

The distance moved by the point of effort is greater than the distance moved by the load.

29
Q

What is the equation for mechanical advantage?

A

Resistance/Effort

30
Q

What is actual mechanical advantage?

A

Tells us how much easier the work can be done.

31
Q

What is the equation for mechanical advantage?

A

Output force/ Input force

32
Q

What is ideal mechanical advantage and what is the equation?

A

Mechanical advantage if there were no resistance in the machine.
Input distance/output distance

33
Q

What is a lever?

A

Rigid bar capable of turning around a fulcrum.

34
Q

What are the parts of the lever?

A

Fulcrum, force and effort.

35
Q

How do you calculate the effort required to lift a weight using a lever?

A

Work out the moments…Effort x length of arm = Resistance x length of arm

36
Q

If a question asks what is the mechanical advantage what steps must you take?

A

Rearrange the opposing moments formula to find effort: F1 = F2 x S2 divided by S1. This will give you the effort which can then be used in MA= R/E.

37
Q

What is a second class lever.

A

Fulcrum at one end rather than in the middle, i.e a wheelbarrow.

38
Q

What is an inclined plane?

A

A surface inclined to a horizontal plane at any angle but 90 degrees.

39
Q

What is a spur gear?

A

Teeth cut straight and used to connect two parallel shafts, they will turn in opposite directions.

40
Q

If you want spur gears to turn in the same direction what must one of them have?

A

Internal teeth.

41
Q

What is a bevel gear?

A

Teeth cut into a conical surface known as the pitch zone.

42
Q

Where are bevel gears used?

A

Transmit forces perpendicular to one another.

43
Q

What is worm gear?

A

Steering rack.

44
Q

When is a worm gear used?

A

When a large reduction in speed is needed and for high toque multiplication.

45
Q

What is the input gear in sun and planet gears?

A

The sun.

46
Q

How does sun and planet gears work?

A

Planet gears are held together by a cage driven around the sun gear and engage at their outer edge in a fixed ring gear which does not rotate.

47
Q

What is the output of a sun and planet gear?

A

The cage which is rotating slower than but in the same direction as the sun.

48
Q

What is an example of a sun and planet gear?

A

Propeller reduction gear.

49
Q

Where are sun and planet gears used?

A

Where space and weight is an issue but a large amount of speed reduction and torque is required.

50
Q

What is efficiency?

A

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

51
Q

Why can’t any machine be 100% efficent?

A

Loses like heat, friction, deflection and wear and tear.

52
Q

What is a third class lever?

A

The effort is applied at the fulcrum. i.e. landing gear.

53
Q

How do you work out the mechanical advantage of gears?

A

Driven gear teeth divided by drive gear teeth.

Cat B- Mod 2 Physics (9 decks)

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