Term
What is inertia, how do we quantify in linear motion? 

Definition
property of a body to resist a change in it's state of motion. We measure it in mass. 


Term
How do we quantify an objects resistance to a change in angular motion? 

Definition
Moment of inertia; unlike its linear counterpart, mass, the moment of inertia depends on mass AS WELL AS the distribution of mass w/ respect to an axis of rotation. 


Term
What is the formula for moment of inertia? (I), units? is moment of inertia fixed or changeable? 

Definition
I = (sum)m*r^2, units: kg*m^2 it is changeable because it can be around different axes 


Term
what is angular momentum formula? 

Definition
H = I * w or = moment of Inertia * angular velocity units: kg m^2 s1 


Term
give examples of how (I) or moment of inertia can change in sports: 

Definition
gymnast: tuck head almost into head to reduce moment of inertia so that can accelerate and finish somersault
runner: LOW moment of inertia when foot near buttocks, high moment of inertia when leg straightened, relative to the lower extremity relative to a transverse axis through the hip joint 


Term
During flight, what are the forces and moments acting on the diver? H? 

Definition
gravity only external force, H remains constant. Conserved during flight b/c BW vector, acting through total body center of gravity, creates no torque. This principle allows divers to mainipulate their moemnts of inertia and angular velocities. 


Term
what determines the quantity of angular momentum before a flight? 

Definition
the torque applied over time at the point of takeoff 


Term
what is the angular analog for newton's first law? second law? 

Definition
first law? conservation of momentum, so "H" stays constant second law? F=ma, so (sum of external)T= I*alpha 


Term
when will an external torque produce angular acceleration? 

Definition
when it is proportional and in the same direction of the torque and inversely proportion to the moment of inertia of the body 


Term
what is the formula for angular impulsemomentum and what is it derived from? 

Definition
Derived from Newton's 2nd law and it is T=(change)angular momentum / (change)in time 


Term
Why are forces exerted by muscles and loads during movement of interest? What kinds of forces do muscles produce? 

Definition
Potential of an activity to cause injury, determining task demands, loads on joints Muscles produce eccentric forces across joints so we use joint torques 


Term
What do we need to calculate inverse dynamics? to calculate joint reaction forces and muscle moments? 

Definition
Full kinematics (filming walking), external forces, accurate anthropometric measures 


Term
In inverse dynamics, we are looking at a dynamic analysis. We then use what formula? 

Definition
(sum)Tz= I*alpha z (in static we use Fx=m*ax) 


Term
If alpha z = 0 the motion is purely _____ 

Definition


Term
If ax=0 and ay=0, the motion is purely 

Definition


Term
If all of these accelerations are , ... 

Definition


Term
Two important points about inverse dynamics: 

Definition
1. we are NOT calculating force in muscle, we are calculating a moment 2. moment is NET JOINT MOMENT 


Term
Discuss the example of a bicep curl 

Definition
bicep brachii most force, triceps active to stabilize. this is example of cocontraction also must consider passive structures like skin, other tendons 


Term
why don't we calculate force of muscles? 

Definition
because there are way too many forces and not enough equations 


Term
How do we obtain kinetic data in inverse dyanmics? 

Definition
Forces acting on system: gravity, GRF, external forces, need to be measured 


Term
What are the 3 types of body segment parameters? 

Definition
Regression equations from cadavers (problem: no blood), mathematical models (geometric solids), imaging and scanning (gamma mass; problem: exposed to radiation, MRI, DEXA) 


Term
What are assumptions when developing a link segment model? (5) 

Definition
1. segment mass is fixed 2. locaiton of CM fixed during movement 3. joints are frictionless hinge (or ball and socket joints) 4. I is fixed at CM and is constant during movement 5. length of each segment is fixed 


Term
What is the proces by reactino forces and muscle moments are calculated is called ____________ 

Definition


Term
If cocontraction is taking place at a joint, what does the analysis yield? 

Definition
the net effect of agonist and antagonistic muslces, and any friction effects also all factored in as as the effective "msucle" moment 


Term
At each hinge joint what do we observe in the FBD's? (Newton's 3rd Law) 

Definition
we see an equal and opposite force acting at each hinge joint. 


Term
what are two areas of investigation for gait? 

Definition
resultant moment of force, and muscle mechanical power, are good diagnostic information 


Term

Definition
net joint moment * joint angular velocity (+)power = concentric muscle action (i.e. flexors)
()power: eccentric muscle action, net moment force occurs in opposite directrion as segment 


Term
Explain the moments throughout gait at the ankle when walking: 

Definition
Initially eccentric dorsiflexion at loading. Followed by net eccentric plantarflexion. Then concentric plantarflexion to push into swing phase. Then small dorsiflexion moment during initiation of swing to keep toe up. 


Term
what is mechanical work equal to? 

Definition
product of magnitude of force applied * distance object moves 


Term
what is the longer equation for work? and units? 

Definition
W= F * cos(theta) * displacement 


Term
does work reflect intensity? what is the rate at which work is being done? 

Definition
no work does not reflect intensity. power is an indicator of intensity, or rate at which work is being done 


Term
what is the formula for power? units!? 

Definition
P = W / t watts (1hp = 746 w) 


Term
Our ability to sustain a given speed depends on what? 

Definition


Term
although humans are not a "powerful" machine what can we do? 

Definition
versatility in how power is applied 


Term
components of human power production, power is a combo of what? 

Definition
strength (ability to produce force) and velocity of movement = F*v 


Term
what did Lanza et. al, 2003 find? Or hypothesize? 

Definition
under isovelocity conditions, older adults slower to reach target velocity, and down shift in torque and power velocity at ankle dorsiflexor and knee extensor muscles 


Term
does the product of F and v have same units as product of T and w? can you prove this? 

Definition
P = W*t = (F*d)/t = F *v watts, Nm/s 


Term
How can we calculate power at the elbow during a bicep curl? (aka muscle power) 

Definition
Net elbow moment, and angular velocity of the elbow joint 


Term
what does the area under a powertime curve equal? 

Definition


Term
what does positive msucle power indicate? 

Definition


Term
what does negative muscle power indicate? 

Definition
eccentric action of the muscle 


Term
describe power and moment in a bicep curl: 

Definition
initial positive muscle power, positive muscle moment, concentric contraction. Then negative muscle power, still flexing but now extensors dominate 


Term
What is the study of fluid mechanics? 

Definition
study of forces that develop when an object moves through a fluid 


Term

Definition


Term
two fluid forces of particular interest? and what are their definitions? 

Definition
drag: or air resistnace, opposes motion of object lift: net force perpendicular to direction of relative motion of the fluid past the object, so perpendicular to the drag force 


Term
two types of drag: which has a greater effect? 

Definition
surface drag (friction): F to V depends on smoothness of surface
form drag (pressure): F to v^2 depends on crosssectional area 


Term
in form drag (pressure), if you are going twice the speed as you were before, how much greater is the Force? 

Definition
4x greater than initially 


Term
when is surface drag referred to in sport, and form drag? 

Definition
swimming shaving, and swimming buoyancy or bicyclist, respectively 


Term
when does lift force occur? 

Definition
when object is spinning, or object not perfectly symmetrical 


Term
according to bernoulli's principle: 

Definition
pressure is inversely proportional to the velocity of air flow 


Term
how does lift force come about in an airplane wing? 

Definition
A and B air molecules move across wing at same time interval, but different distances. Thus top of wing air moves faster, resulting in lower pressure, resulting in lift force 


Term
how does the magnus effect work? 

Definition
baseball players mastered just enough spin so that they can decide which side of the ball has more or less pressure, thus the direction of the curve 


Term
what are the angular analogs of force, mass and acceleration respectively? 

Definition
torque, moment of inertia, and angular acceleration 

