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kin 222 > midterm 2 > Flashcards

midterm 2 Flashcards

1
Q

angular position (normal, absolute, and relative)

A

angular position: orientation of a line with another line or plane

absolute: angle of a single body segment with respect to a known vertical or horizontal

relative: angle of one segment relative to another.
specifically the angle between longitudinal axes of two segments

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2
Q

absolute segment angles

A

calculated using the trigonometric relationship: tangent= opposite over adjacent

to calculate absolute leg angle: proximal segment coordinate values are subtracted from the distal end coordinate values
the ratio of y to x defines the tangent of the angle

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3
Q

relative angles how to calculate?

A

law of cosine: side of the traingle that dont contain a right angle

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4
Q

axis rotation
rigid body

A

axis rotation: fixed line about which a rigid body rotates
always perpendicular to its plane
sagital ml
frontal ap
transverse lognitudinal

rigid body: a body that maintains a constant shape when rotated (bones)

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5
Q

right hand rule

A

clockwise is negative
counterclockwise is positive

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6
Q

angular distance vs displacement

A

angular distance: sum of all angular changes (scalar)

angular displacement: difference between the final and initial positons (vector)

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7
Q

linear vs angular displacement

A

when an object or rigid body rotates, it undergoes both linear and angular displacement

linear displacement of a point on a rotating object or rigid body is directly proportional to the distance that point is from the axis of rotation
greater the radius: greater the linear displacement

linear is related to angular but not proportional to it

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8
Q

angular speed vs velocity

A

angular speed: is the angular distance travelled per unit of time (scalar)

angular velocity: charaterized by the Greek letter omega (w), is a vector quantity that desribes the time rate of chnage of angular position (rad/s or degrees/s or rpm)

angular velocity= angular displacement divdied by time

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9
Q

angular acceleration

A

angular acceleration= a greek letter alpha
rate of change in angular velocity measured in radians per second squared (rad/s 2) or in degrees per second squared

a= w/t

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10
Q

angular kinematics

A

angular motion occurs when all parts of the body move through the same angle but do not undergo the same linear displacement

the subset of kinematics that deals with angular motion is angular kinematics, which describes angular motion without regard to the causes of the motion

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11
Q

unit of measurement (degreee, revolution/ # of rotations, radian)

A

degree: one circle/one complete= 360 degrees

revolution/# of rotations: one circle= one revolution

radian: one circle= 2 pie radians
1 rad= 57.3 degrees

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12
Q

force

A

vector quantity: magnitude and direction
what does it do? a force involves the interaction of two objects and can produce a change in the state of motion of an object by pushing or pulling it

force= mass x acceleration

unit: newton (N)
1N= Amount of force it takes to accelerate a 1kg body at 1m/s 2
often represented as a ratio of force to body weight (BW)= %BW

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13
Q

newtons three laws of motion

A

1) law of inertia: a body will remain at rest or continue to move with a constant velocity unless acted upon by an outside force

inertia: used to describe an objects resistance to motion and is directly related to the mass of a object

newtons second law
law of acceleration:
f=ma explains the effect of the net force
net force= mass x acceleration
unit of force is newtons (N)
* a force applied to a body causes acceleration of that body:
of a magnitude proportional to the force
in the direction of the net force ex) tug o war
and inverslet proportional to the bodys mass

Newtons 3rd law: action/reaction
for every action there is an equal and opposite reaction
force always acts in pairs
these paired forces are equal and opposite

jumping off the ground
indvidual exerts force on ground
ground exerts force on the individual

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14
Q

inertia what is it?
how to overcome it?

A

used to describe an objects resistance to motion and is directly related to the mass of an object
inertia your acceleration will be 0 due to having a constant velocity
overcome inertia, to get something to move, the force needs to be greater than the inertia/mass of object

if this occurs, the object will be accelerated in the direction of the applied force

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15
Q

momentum

A

momentum (P): the quantitiy of motion of an object
product of the objects mass and linear velocity
the faster an object moves with more mass, the greater the momentum

p=m x v

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16
Q

accleration

A

a force applied to the body causes an acceleration of the body

of a magnitude proportional to the force
amount force applied= amount acceleration felt on object

in the direction of the net force

and inversely proportional to the bodys mass

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17
Q

rearranging newtons second law (acceleration)

A

F= ma
f= m x v/t
f= m x v / t

p= m x v

force is equal to to the time rate of change of momentum

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18
Q

conversion of momentum

A

in the absence of external forces momentum is constant

only external forces will change the motion of a system

example
two people colliding but not bouncing off each other
means both momentums would equal 0 because momentum before would be the same as momentum after

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19
Q

impulse

A

linear impulse is the product of a force and the time interval over which a force acts
change in linear momentum

I= Ft
I= P2-p1 or m2v2 - m1v1

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20
Q

tangential vs centripetal

A

tangential: acceleration tangent to the rotation segement

centripetal: acceleration along the segement towards the axis

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21
Q

body weight and mass are different

A

body mass is scalar
body weight is a vector

22
Q

main types of force

A

gravity
ground reaction force
friction
fluid resistance
joint reaction forces
inertial force
muscle force
elastic force

23
Q

ground reaction force

A

the weight of a person standing in the anatomical neutral position generates a reactor force by the ground that is equal in magnitude and opposite in direction to the weight
external force acting on the body

24
Q

propulsive force
breaking force

A

propulsive force: a fore that is causing a body to speed up

breaking force: a force that is causing a body to slow down

25
Q

GRF in walking vs running

A

walking: max vertical GRF = 1-1- 1.2 BW
one peak for 1st half of support, valley during knee flexion at full support, then second peak as push off the ground

running: maximum vertical GRF component= 2-5 BW
shape depends on footfall pattern of runner

26
Q

friction

A

a force that acts parallel to the interface of two surfaces that are in contact during motion (impending motion)
direction is opposite of motion
ex: block sliding on a flat surface slide
pulling force needs to be greater than the friction force

friction= coefficient of friction x normal force

27
Q

kinetic friction
static friction

A

friction that allows movement= kinetic friction
kinetic friction is less than the static friction and changes according to the speed of object

friction that is large enough to disallow movement= static friction

28
Q

normal force

A

is the force perpendicular to the surface

29
Q

inertial force

A

one body segment can exert force on another segment , causing movement at that second segment without muscle exertion

typically a more proximal segment exerts an inertial force on a more distal segment

29
Q

coefficient of friction

A

unitless number
indicates the relative ease of sliding.
greater coefficient= harder to slide (carpet)
less coefficient= easy to slide (water, ice)

30
Q

friction in athletic contects

A

skaters like fresh ice low coefficient because easier to slide

golfers wear gloves to increaase coefficient of friction and get a better grip on the club

30
Q

fluid resistance

A

air resistance
water resisitance

both greatly affected by two components:
ex: density of air greatly affected by humidity, temperature, pressure

viscosity: (a measure of the fluids resistance to flow)
water is more viscous than air

drag force: always act to oppose the motion
lift force: always afcts perpendicular to the drag force
produced by a break in the symmetry of airflow
seams on a ball

31
Q

joint reaction forces

A

segments are often analyzed separtely
ex) while standing still, at the knee joint you can examine:
the upward force of the lower leg on the thigh
the downward force of the thigh on the lower leg

net force across the knee joint: joint reaction forces

31
Q

muscle force

A

muscle can generate only a pulling force
ex: the biceps brachii can pull on its insertion on the forearm to felx the elbow
ex: the triceps brachii can pull on itds insertion ont he forearm to extend the elbow

32
Q

static equilbrium

A

no acceleration
system is at rest or at constant velocity

example tug a war

32
Q

elastic force

A

force applief to a material can result in a change in length in that material

F= k s
k=stiffness
s= change in length

ex: diving board

33
Q

work: effect of force applied over a distance

A

work: the product of the magnitude of the force applied to an object and the distance the object moves in the direction of applied force
unit joule (j) or newton-meter (Nm)

w= f x d or w= f x cos x s

34
Q

directional work

A

the object is moved in the same direction of force

negative work: the object is moved in the opposite direction of the force

cocentric= + work
eccentric= - work

35
Q

power

A

the amount of wokr done per unit of time (the rate of mechanical work)
units is watts (w) or 1 j/s

P= w/t

greater power is quicker

36
Q

power can also be seen as force x velocity if you rearrange

A
37
Q

simultaneous kinetic chain linking
sequential kinetic chain linking

A

simultaneous; activation of multiple muscle groups and segments at the same time
ex) power clean

sequential: activation of muscle groups and segments at different times throuhgout the movement
ex) baseball throw

38
Q

energy

A

capacity to do work
various types of energy: light, heat, nuclear, elctrical and mechanical

two main types of mechanical energy:
kinetic: refers to the energy resulting from motion
potential: refers to the capactiy to do work because of position or form.
an object may contain stored energy, for example, simply becasue of its heigh or its deformation

39
Q
A
40
Q

kinetic energy

A

KE= 1/2 mv squared

Ke is the ability of a moving object to do work resulting from its motion
0 velocity= no KE
change in velocity= great increase in KE

41
Q

potetntial energy

A

energy due to an objects position (capacity to do work)
PE= Wh (weight x height)
PE= mgh (mass x gravity x height)

42
Q

total energy= KE + PE

A
43
Q

COM location

A

human body is not a rigid object so the location depends on position of extremtities

44
Q

importance of COM

A

stability: resistance to linear and or/ angular acceleration \

balance: ability to control equilibrium. in order to balance, the athletes COM must be located within the support base.

45
Q

principles of stability
how to improve stability

A

increase body mass
increase friction between the body and contact surface
increase size of support base in the direction of the line of action of the external force
horizontally position COM near the edge of support base on the side of oncoming external force (no external force than COM in middle of support base)
vertically positioning COM as low as possible (linebacker)

46
Q

pressure

A

force per unit area
1 N per m squared equal to 1 pascal
units pascal (Pa) and kilopascal (KPa)

P= f/a

kin 222 (2 decks)

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