Mechanical Principles Midterm (test 2) Flashcards by Mariah Wagner

Things that affect drag:

Increased air temp
Increased humidity
Increased altitude

All Decrease air density and drag

How well did you know this?

Not at all

Perfectly

Drag definition

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

Drag forces always act in opposite direction

How well did you know this?

Not at all

Perfectly

Surface drag def

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

How well did you know this?

Not at all

Perfectly

When does skin friction of surface drag increase

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

How well did you know this?

Not at all

Perfectly

Laminar flow

Smooth, parallel layers of fluid

How well did you know this?

Not at all

Perfectly

Turbulent flow

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

How well did you know this?

Not at all

Perfectly

What is Form drag derived from

Aka profile drag and pressure drag

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

How well did you know this?

Not at all

Perfectly

What does the rear side of form drag create

A wake from swirling low pressure or turbulence

How well did you know this?

Not at all

Perfectly

What does a streamlined shape due to form drag

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

How well did you know this?

Not at all

Perfectly

Form drag increases when

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

How well did you know this?

Not at all

Perfectly

Wave drag def

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

How well did you know this?

Not at all

Perfectly

Which sports does wave drag effect?

Sports with lots of up and down movements

Breaststroke, Butterfly, boating

How well did you know this?

Not at all

Perfectly

Wave drag wave created in front is what

A high pressure wall the resists forward movement

How well did you know this?

Not at all

Perfectly

Wave drag increases with:

Vertical oscillation of the body with respect to fluid

Relative velocity of the body in fluid

How well did you know this?

Not at all

Perfectly

Wave drag decreases when:

Stay under water as long as possible

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

How well did you know this?

Not at all

Perfectly

Wave drag in swimming

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

How well did you know this?

Not at all

Perfectly

Lift

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

How well did you know this?

Not at all

Perfectly

Resultant force equation

Resultant force= lift+ drag

How well did you know this?

Not at all

Perfectly

Lift increases with

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

How well did you know this?

Not at all

Perfectly

Bernoulis principle

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

Regions of low pressure are associated with regions of high pressure

Creating lift

Bs principle + newtons 3rd law

Increased air pressure below the airfoil

Air is directed downward on the upper and lower surfaces

Magnus effect

Pressure differential created by a spinning body

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

What is a Fluid?

Both liquids and gases are fluids

What are fluids that commonly exert forces on the human body

air and water

Fluid Properties

Density - mass/volume | Viscosity – how thick the fluid; how much it clings

Hydrostatic Pressure def

Force exerted by a fluid (air or water)

Buoyancy def

Tendency for something to float

What direction is buoyant force?

always vertically upward, against gravity:

Example of buoyancy

torso is easier to float than legs bc more buoyant

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

body will rotate

balance def

The ability to control equilibrium | Ability to keep the center of gravity (line or gravity) within their base of support (most of the time)

stability def

Amount of resistance used to prevent the loss of balance | Maintaining the line of gravity within the base of support

example of balance, good stability

sumo wrestler in low stance

example of good balance but bad stability

ballerina on toes

linear stability def

Resistance to being stopped or having direction changed

linear stability relation to mass

directly related. more mass more linear stability

Consequence more mass;

greater inertia to start movement and change direction

Rotary stability def

Resistance to being tilted, tipped-over, or spun

which sports use rotary stability the most?

grappling arts such as wrestling and judo

What must you maintain for rotary stability?

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

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

greater greater harder

Opposing forces that jeopardize stability of rotary stabiliity

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

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

any part of the body or the opponents body

Maximizing stability

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

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

the center of base of support

When anticipating an oncoming force | shift......

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

How do you Lower COG

Spread base of support wide in direction of oncoming force

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

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

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

its oscillating between stable and unstable conditions