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General Explanations (Written) > Basic Physics > Flashcards

Basic Physics Flashcards

1
Q

The force a hydraulic actuator can exert is determined by what?

A

The area of the piston and the pressure of the fluid acting on the piston.

F = P x A

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2
Q

Heat can be transferred from a body of high heat energy levels to a body of lower heat energy levels by what three methods?

A

Conduction

Convection

Radiation

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3
Q

What is conduction?

A

Heat transfer through actual physical contact

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4
Q

What is convection?

A

Heat transfer through vertical currents (hot air)

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5
Q

What is radiation?

A

Heat transfer by electromagnetic waves (the sun)

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6
Q

Work equation

A

Work = Distance x Force

Work is measured in foot pounds

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7
Q

What is absolute humidity and what is it measured in?

A

The actual amount of water in a volume of air, and it is measured in grams per cubic meter.

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8
Q

Water vapor is about how much lighter than an equal volume of air?

A

Water vapor is about 5/8ths as heavy as an equal volume of air. The more water vapor in the air, the less the air weighs.

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9
Q

What is relative humidity?

A

The ratio of the amount of water vapor actually present in the atmosphere to the amount that would be present if the air were saturated at the prevailing temperature and pressure.

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10
Q

How does the pressure of a gas in an enclosed container vary with the volume of the container (if the absolute temperature of the gas remains constant)?

A

The pressure varies inversely with the volume.

P = T / V

Doubling the volume of a container will decrease the pressure of the enclosed gas by half

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11
Q

What is pressure differential?

A

The difference between pressures being read at two different locations within a system.

For example, the pressure read before oil enters an oil filter will be greater than the pressure read after it passes an oil filter, which provides a degree of resistance to the rate of flow. The drop in pressure will be the pressure differential.

Study guide question 8470, pg. 106

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12
Q

What is the advantage of a single fixed pulley?

A

Use to change the direction of applied force.

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13
Q

What is the advantage of a multiple movable pulley?

A

Used to provide a mechanical force equal to the number of support ropes.

Example: A multiple movable pulley with four support ropes has a MA of 4:1.

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14
Q

How does the speed of sound vary with temperature?

A

Directly. The higher the temperature, the faster the speed of sound.

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15
Q

What is absolute humidity?

A

The actual amount of water vapor in a mixture of air and water.

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16
Q

Will the volume of a liquid change with a change in pressure?

A

No. Liquids are considered to be non-compressible, so its volume will stay the same regardless of the pressure.

However, the volume will change with a change in temperature.

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17
Q

The true landing speed of an aircraft is determined by what?

A

The density of the air.

The less dense the air, the faster the plane will have to fly to produce sufficient lift during a landing.

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18
Q

The amount of lift produced by the wing of an airplane (or the rotor of a helicopter (helicopter? gross)) is determined by what?

A

The shape of the airfoil

The speed of the airfoil through the air

The density of the air.

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19
Q

What does the density of the air depend on?

A

Temperature, the hotter the air, the less dense it will be.

Humidity, the more water vapor in the air, the less dense it will be.

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20
Q

Power equation

A

Power = Work / Time Required

or

Power = (Force x Distance) / Time Required

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21
Q

What is a first class lever?

A

when the fulcrum is located between the effort and resistance.

22
Q

Mechanical advantage equation for first, second, and third class levers.

A

MA = R / E = L / I

or

MA = E x L = R x I

MA = Mechanical Advantage
R = Weight of object to be raised or lowered
E = Force required to raise or lower object
L = Distance from fulcrum to effort
I = Distance from fulcrum to resistance

23
Q

What is a second class lever?

A

When the resistance is located between the fulcrum and the effort.

24
Q

What is a third class lever?

A

When the effort is located between the fulcrum and the resistance.

25
Q

Gears mechanical advantage equation

A

MA = driven teeth / drive teeth = drive rpm / driven rpm = driven torque / drive torque

26
Q

What is the purpose of an idler gear?

A

The purpose of an idler gear is to allow the driven and drive gear to rotate in the same direction. It doesn’t change the mechanical advantage, rpm, or torque.

27
Q

Incline plane (ramp) equation

A

MA = Run (L) / Rise (I)

or

MA = R / E = L / I

MA = Mechanical Advantage
R = Weight of object to be raised or lowered
E = Force required to raise or lower object
L = Length of ramp, measured along the slope
I = Height of ramp

28
Q

Heat is a form of energy, and temperature is a measure of what?

A

The intensity of the kinetic energy of the molecules in a substance.

29
Q

What is dewpoint?

A

The temperature to which a body of air must be lowered before the water vapor in the air condenses out as visible, liquid water.

30
Q

The pressure exerted by a confined gas is directly proportional to what?

A

Its absolute temperature.

If the temperature is doubled, the pressure will also double.

31
Q

The pressure exerted by a confined gas is inversely proportional to what?

A

Its volume.

If its volume is doubled, the pressure will decrease to a value that is one half of the original.

32
Q

What are stall strips?

A

small triangular spoilers, or wedges, attached to the leading edge in the root area of a wing that has a tendency to stall at the tip before the root.

33
Q

What is the benefit of a stall strip?

A

Stalls starting at the tip of a wing rather than the root cause a loss of aileron effectiveness, and therefore lateral control, when it is most needed.

At high angles of attack, stall strips disrupt the airflow over the wing root and force it to stall before the portion of the wing ahead of the aileron.

If all or a significant part of a stall strip is missing, the stall on the affected wing will begin near the tip and decrease the effectiveness of the aileron, requiring asymmetrical lateral control at or near the stall angle of attack. More aileron deflection will be need to raise the wing with the missing stall strip than the wing with the intact strip.

34
Q

How is aerodynamic lift produced?

A

by the pressure differences across the airfoil along with with the downward deflection of air. The pressure below the wing surface is greater than that above the wing. The pressure below the wing may be considered positive and that above the wing negative.

35
Q

What is Newton’s first law of motion?

A

Objects at rest tend to remain at rest and objects in motion tend to remain in motion at the same speed and in the same direction, unless acted on by an external force.

(inertia)

36
Q

What is Newton’s second law of motion?

A

Force is proportional to the product of mass and acceleration. When a force acts upon a body, the momentum of that body is changed.

37
Q

What is Newton’s third law of motion?

A

To every action, there is an equal and opposite reaction. If a force is applied to an object, the object will supply a resistive force exactly equal to and in the opposite direction of the force applied.

38
Q

What is wing dihedral and what is its purpose?

A

dihedral is the upward slant of the wing from the fuselage to the wing tip.

It is used to increase lateral stability, and naturally return the plane to level flight.

39
Q

What is lateral stability?

A

Rotation around the longitudinal axis, controlling roll.

40
Q

What is longitudinal stability?

A

Rotation around the lateral axis, controlling pitch.

41
Q

What is the aspect ratio of a wing?

A

The ratio of the wing span to the mean, or average, chord.

42
Q

How is aspect ratio found for a non rectangular wing?

A

For a nonrectangular wing, aspect ratio is found by dividing the square of the wing span by the wing area.

Aspect Ratio = wing span^2 / wing area

43
Q

Wings with a high aspect ratio have what?

A

Low drag at high angles of attack, low stalling speed, and good control at low airspeeds.

Sailplanes have very high aspect ratios and fly slowly.

44
Q

What is a wingtip and what is its purpose?

A

Small upturned vertical surfaces mounted on the wing tips.

They reduce drag by reducing the spanwise flow of air, therefore reducing vortices. The desired effect of using winglets on an aircraft’s wingtips is to increase the lift to drag (L/D) ratio of the wing.

45
Q

The classification of main rotor systems is based on what?

A

How the blades move relative to the main rotor hub.

46
Q

What are the three principal classifications of a main rotor system?

A

fully articulated, semi-rigid, and rigid.

47
Q

What are the primary flight controls on a helicopter?

A

The collective and cyclic control levers and anti-torque pedals.

48
Q

What happens when the collective pitch control lever is raised?

A

The blade angle of all the rotor blades increases uniformly and they create the lift that allows helicopters to take off vertically.

49
Q

How does the cyclic pitch control lever operate?

A

Like the yoke of an airplane. It can be pulled back or pushed forward (for backward or forward motion), and can be moved left and right (to bank left or right)

50
Q

The boiling point of a liquid varies directly with what?

A

The pressure above the liquid. The greater the pressure, the higher the boiling point

General Explanations (Written) (12 decks)

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