Friction and Traction

Why are you most likely to slip at the beginning or end of a step

because the horizontal force is higher than the vertical force

friction and traction can be

both linear and angular

what is the most common turf used

both monofilament and slit film

what is the newest turf

both monofilament and slit film with thatch

what force must we keep through our COM in order to avoid toppling

GRF

Traction

The propulsive or breaking force generated on the spot surface by an athlete

what is the Us for soil/granular surface with cleats

can be greater than 1

what is required for a banked turn

centripetal acceleration

what does shock absorption help with

comfortability and injury prevention

geofill

conconut husks

What type of friction force exists in dynamic friction

constant friction

which performance layer degrades too quickly

cork

what is the most common performance layer infill

crumb rubber

what are the types of performance infill

crumb rubber, virgin rubber, brockgill, geofill, safeshell, envirofill

what is thatch

curly plastic fiber under sand to hold infill in place

What is the coefficient of friction independent of

deformation and velocity of sliding

point elastic

deformation isolated to contact area

slit flim

designed to fray

how does static friction and dynamic friction compare to each other

dynamic is less than static which is less than 1

why is slit film not used by itself anymore

its mats up and creates to much interlocking

What is important to note about tribology

its not all about decreasing friction with ball bearings

large accelerations means

large force

The faster you run the more you need to

lean

what does third generation turf look like

longer blades of grass woven into packing with a sand and performance layer and occasionally a shock pad

what is the utilized COF

max ratio during stance phase

What do coulomb conditions depend on

moisture, adhesion, dust/small particles, contact area, deformation

what are the different types of grass fibers for turf

monofilament, slit film, both, both and thatch

Do coulombs conditions exist

more hypothetical than real

what is the issue with turf

more lower limb injuries on turf

What so we need to do when looking at friction diagram

need to resolve the interaction force into components normal and tangent to the sureface

does normal force change the coefficient of friction

no

Static friction

no relative motion

Is the normal force always weight

no, in a dynamic situation the vertical GRF may be below or above our weight

what type of deformation does soil/granular surfaces have

non-linear and irreversible (permanent deformation)

which type of hard surface deformation changes the friction component

point elastic

what are the types of hard surface deformation

point elastic and area elastic (mixed elastic and combined elastic)

What is smoothness/roughness referring to

properties of both objects and how they interact

what does an incline do in regards to banked turns

reduce friction needs in horizontal direction

what is the shear zone

root zone hasn't been fully developed yet

enviorfill

rubber coated sand

Hard surface deformation influences

shock and energy absorption/return

what affects deformation

shoe/foot and hard surface vs soil/granular

monofilament

single think blade

Dynamic friction

sliding exists

What is friction force dependent on

smoothness/roughness, normal force between objects, if sliding exists

area elastic

some deformation of floor (larger area)

what type of deformation doe grass have

somewhat permanent deformation

What are the types of relative (sliding) motion

static friction and dynamic friction

what matters with cleats and soil/granular surfaces

surface area

what is the max static friction

the force to start sliding

When pushing an object on an incline, what must you over come

the gravitational force and frictional force

How does height effect toppling

the lower your COM is to the ground, you will topple less

the higher the utilized COF

the more likely you are to slip

What partially generates the centripetal acceleration on a banked turn (on an incline)

the normal force

What is required to maintain traction

the ratio GRFx/GRFy less than Us

Tribology

the study of friction, wear, lubrication, and the design of bearings; the science of interacting surfaces in relative motion.

what is 1 equal to in coulomb conditions

the weight of the ojbect

When pushing the a sled more up what happens

there is a decrease in the GRF acting against you

when 3rd generation does not have a shock pad, what is done

thicker blades of grass and more infill

crumb rubber

tire

why is traction needed for

to react and move quickly (accelerate and decelerate)

descrie divits

traction is lost when the surface fails at the shear zone

If there is no slope on a banked turn, how do we produce the centripetal force

using the friction force

virgin rubber

various

safeshell

walnut shells

As the angle increase, what happens to the force we must produce

we must produce more and more force

When does traction apply

when one of the bodies has the ability to develop its own power while it attempts to gain motion

How do you achieve the sum of torques about your COM equaling 0

when the GRF acts through the COM

when will an object stop sliding

when the force applied is less the Fd

When do we lose traction

when the numerator (GRFx) is higher than the denominator (GRFy)

What is traction associated with

with friction and other forms of foot-surface interaction

brockFILL

wood

In coulomb conditions, what is the max that frictoin can be

1

Friction

Force opposing direction of impending motion due to interaction with another surface

what is the equation for the coeffiecnt of friction

Friction Force/ Normal Force

the pushing force on an incline gets harder and harder to what point

about 45 degrees

in order to stay on curve

accelerate at angle

what does centripetal acceleration allow for banked turns

allows for easier development of horizontal forces

which type of had surface deformation has better shock absorption

area elastic

What was the early turf

astroturf- think layer of carpet over concrete

When are you most likely to slip

at the beginning or end of a step

In order to keep ourselves from toppling, out sums of torque about COM must be what

equal to 0

describe natural turf/grass surfaces

fiber reinforced soil/granular surfae

Use of cleated footwear violates notion of

friction being responsible got traction

in regards to an incline angel increase, describe the way frictional and gravitational force decrease

gravitational force increases at a faster rate than frictional fore

what force is always acting though your COM

gravity

describe the horizontal force and vertical force in traction

horizontal force is higher at beginning and end while vertical is higher in the middle

what is not needed in dynamic conditions

how fast it is sliding

what is dynamic independent of

how fast the sliding is

earlier we said that coulombs conditions are not affected by contact higher, why is that different here

in extreme conditions (such as a lot or very little contat area) makes a small impact

what type of nature do cleats have with soil/granular surfaces

interlocking nature (to creat friction)

How is friction added in natural turf/grass with cleats

interlocking nature of both grass and soil

As the incline angle increase, what happens to the frictional force

it decreases

As the incline angle increases, what happens to the gravitational force

it increases

how does the coefficient of static friction change as applied force increase

it increases lineraly

how does the coefficient of dynamic friction change as applied force increase

it stays the same