# Shared Flashcard Set

Biomechanics
Exam 2
27
Physiology
10/25/2011

## Additional Physiology Flashcards

Term
 What is momentum?
Definition
 quantity of motion, keep on goingp=mvunits= kg*m/s
Term
 Describe Newton's 2nd law in terms of momentum:
Definition
 rate of change of momentum with respect to time produced by the force
Term
 What is the equation of Newton's 2nd law in terms of momentum?
Definition
 (sum of)F= (mvf-mvi) / (change in)t
Term
 What is impulse?
Definition
 It is the measure required to change the momentum of an object. Unit (N*s)
Term
 how can we manipulate the impulse-momentum relationship i.e. in terms of injury prevention?
Definition
 impulse is the shaded area under a force-time curve. we can manipulate this relationship by changing the time and/or force, aka a large force over a short time or small force over a large time
Term
 what are examples of spreading an impact out over time?
Definition
 catching an egg, landing from a vertical jump, crumple zone, function of a bike helmet
Term
 draw what the forces loook like for walking and running. what are characteristics of these two graphs? what about the AP force?
Definition
 running: has two peaks (impact peak and active peak). the propulsion phase is less than the breaking phasewalking: bimodal phases (2 max)the AP GRF component has a similiar shape in walking and running; (-)AP is a result of a backward horizontal friction, (+)AP phease is near midstance where force is generated by musc pushing against the ground
Term
 where is the center of pressure?
Definition
 indicates the resultant GRF vector, describes location of centroid of pressure distribution
Term
 when is a force a centric force?
Definition
 when a force is applied to an object so that its line of action passes through the object's center of gravity, or a fixed axis of rotation**AS LONG AS IT IS FREE TO MOVE!!!
Term
 what is an example of a centric force?
Definition
 pushing a desk straight, linear motion
Term
 when is a force an eccentric force?
Definition
 if the line of action of force is "off center", change in angular AND linear motion at times
Term
 give an example of an eccentric force:
Definition
 pushing a wheel of a bicycle, it will spin, if the bike is upside down and locked into the floor
Term
 How do these forces relate to our skeletal system?
Definition
 All muscle forces are eccentric; no muscle passes thru the axis of the joint, therefore it produces angular motion of our joints
Term
 define torque
Definition
 torque, or a moment of force, is the product of the applied force causing a rotation, and the perpendicular distance to its line of action."It is the turning or rotational effect of an eccentric force"!!!it is the tendency of a force to cause a rotation about a specific axis
Term
 is a torque a force?
Definition
 NO! it is the effect of a force in causing a rotation
Term
 what are the units for torque?
Definition
 N-m
Term
 what are two other names for (d)perpendicular?
Definition
 either the torque arm or the moment arm
Term
 M = F * d(perp) is the same equation as T (torque) = F * r (perp distance)
Definition
Term
 what is the moment arm?
Definition
 also d(perp), the moment arm is the perp distance from the line of action of the force to the axis of rotation
Term
 if you were given 3 of the same forces at different angles, which force would be most effective?
Definition
 the one with the longest d perpendicular because that means the greatest torque
Term
 How do you calculate the turning effect due to a force?
Definition
 torque
Term
 what are the conditions for static equilibrium?what must you do first when calculating static equilibrium? and then what?
Definition
 (sum)F=0, (sum)Maxis=0, so Mcw=Mccwcalculate ALL moments firstfind sum of moments afterso essentially (sum)CCW(+)=(sum)CW(-)
Term
 is muscle moment arm greater or smaller than d(perp) of external force?
Definition
 much smaller! think of your flexors insertion, and then think of the dumbbell far away
Term
 How much more is muscle force than weight of dumbbell? Why are we built the way we are, why not longer d(perp)?
Definition
 about 8 times larger or moreand we would have to reposition the orgin or insertion (aka wings)small amount of shortening for large angular displacement
Term
 dynamic situations:does the moment due to the weight of the dumbbell stay the same during a bicep curl? what is the position when d is minimized or maximized?
Definition
 NO! no because the moment arm is changingd(minimized) is either straight or all the way flexedd(max) is 90 degrees
Term
 dynamic situations:does the moment due to the force produced by the muscle stay the same during the bicep curl?
Definition
 no... changes as moment due to weight of dumbbell changes, also muscle moment arm changes
Term
 Looking at a GRF walking, running, graph, talk about BW, magnitude, time
Definition
 BW in walking is 1x as great BW, running is 2-5x as greatmagnitude: vary as a function of locomotor speed, so increase when running
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