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All classes > Mechanical Principles Midterm (test 2) > Flashcards

Mechanical Principles Midterm (test 2) Flashcards

0
Q

Things that affect drag:

A

Increased air temp
Increased humidity
Increased altitude

All Decrease air density and drag

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1
Q

Drag definition

A

Collection of fluid forces that tend to oppose the actions an athlete is performing

Drag forces always act in opposite direction

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2
Q

Surface drag def

A

Aka skin friction or viscous drag

Drag derived from friction between the fluid Nd the object passing through the fluid boundary layer.

It is layer of air or water in direct contact with athlete

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3
Q

When does skin friction of surface drag increase

A

When relative velocity of fluid flow increases
Surface area of body over which the flow occurs increases
Increase the roughness of body surface
Increase the viscosity of fluid

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4
Q

Laminar flow

A

Smooth, parallel layers of fluid

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5
Q

Turbulent flow

A

Mixing of adjacent fluid layers and partial loss of the boundary layer

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6
Q

What is Form drag derived from

A

Aka profile drag and pressure drag

Derived from a pressure differential between the lead and read sides of a body moving through a fluid

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7
Q

What does the rear side of form drag create

A

A wake from swirling low pressure or turbulence

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8
Q

What does a streamlined shape due to form drag

A

Reduces form drag by reducing the turbulence created at the trailing edge

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9
Q

Form drag increases when

A

Increase in relative velocity of fluid flow
Magnitude of the pressure gradient between the front and rear ends of the Body increase
Surface area of the body perpendicular to the fluid flow increases

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10
Q

Wave drag def

A

Drag derived from the generation of waves at the interface between two different fluids, such as air and water

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11
Q

Which sports does wave drag effect?

A

Sports with lots of up and down movements

Breaststroke, Butterfly, boating

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12
Q

Wave drag wave created in front is what

A

A high pressure wall the resists forward movement

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13
Q

Wave drag increases with:

A

Vertical oscillation of the body with respect to fluid

Relative velocity of the body in fluid

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14
Q

Wave drag decreases when:

A

Stay under water as long as possible

Get as far out of the water as possible (hydroplane)

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15
Q

Wave drag in swimming

A

Swimmers want to make minimal wave
More prominent in open water swims
Lane lines minimized wave drag by dissipating moving surface water

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16
Q

Lift

A

A force acting on a body in a fluid in a direction perpendicular to the fluid flow

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17
Q

Resultant force equation

A

Resultant force= lift+ drag

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18
Q

Lift increases with

A

Increase velocity of fluid, surface area of flag side of foil, density of fluid

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19
Q

Bernoulis principle

A

Inverse relationship between relative velocity and relative pressure In a fluid flow

Regions of low pressure are associated with regions of high pressure

20
Q

Creating lift

A

Bs principle + newtons 3rd law

Increased air pressure below the airfoil

Air is directed downward on the upper and lower surfaces

21
Q

Magnus effect

A

Pressure differential created by a spinning body

Deviation in trajectory of a spinning object toward the direction of spin

22
Q

What is a Fluid?

A

Both liquids and gases are fluids

23
Q

What are fluids that commonly exert forces on the human body

A

air and water

24
Q

Fluid Properties

A

Density - mass/volume

Viscosity – how thick the fluid; how much it clings

25
Q

Hydrostatic Pressure def

A

Force exerted by a fluid (air or water)

26
Q

Buoyancy def

A

Tendency for something to float

27
Q

What direction is buoyant force?

A

always vertically upward, against gravity:

28
Q

Example of buoyancy

A

torso is easier to float than legs bc more buoyant

29
Q

what will happen to floating body until buoyant force and weight force are vertically aligned?

A

body will rotate

30
Q

balance def

A

The ability to control equilibrium

Ability to keep the center of gravity (line or gravity) within their base of support (most of the time)

31
Q

stability def

A

Amount of resistance used to prevent the loss of balance

Maintaining the line of gravity within the base of support

32
Q

example of balance, good stability

A

sumo wrestler in low stance

33
Q

example of good balance but bad stability

A

ballerina on toes

34
Q

linear stability def

A

Resistance to being stopped or having direction changed

35
Q

linear stability relation to mass

A

directly related. more mass more linear stability

36
Q

Consequence more mass;

A

greater inertia to start movement and change direction

37
Q

Rotary stability def

A

Resistance to being tilted, tipped-over, or spun

38
Q

which sports use rotary stability the most?

A

grappling arts such as wrestling and judo

39
Q

What must you maintain for rotary stability?

A

Need to maintain COG (line of gravity) within the base of support

40
Q

The BLANK the COG is outside the base of support, the BLANK the torque gravity produces, and the BLANK it is to recover

A

greater greater harder

41
Q

Opposing forces that jeopardize stability of rotary stabiliity

A

Gravity
Wind
Another body (may or may not be human)

42
Q

When destabilized in rotary stability, what can be the axis of rotation?

A

any part of the body or the opponents body

43
Q

Maximizing stability

A

Wider base
Lower COG
Greater mass; also greater inertia to start and change directions

44
Q

where does COG’s Line of gravity (LOG) fall within

A

the center of base of support

45
Q

When anticipating an oncoming force

shift……

A

COG/LOG to the edge of the base of support that is closest to the oncoming force

46
Q

How do you Lower COG

A

Spread base of support wide in direction of oncoming force

47
Q

To produce great force and or velocity in a specific direction:

A

Widen the base of support in the direction of the force output to aid in force output and to maintain balance.

48
Q

What is going on with your stability as you are running or walking?

A

its oscillating between stable and unstable conditions

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