Term
|
Definition
quantity of motion, keep on going
p=mv
units= 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
|
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 phase
walking: 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
|
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
|
Definition
| NO! it is the effect of a force in causing a rotation |
|
|
Term
| what are the units for torque? |
|
Definition
|
|
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
|
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
|
|
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=Mccw
calculate ALL moments first
find sum of moments after
so 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 more
and 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 changing
d(minimized) is either straight or all the way flexed
d(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 great
magnitude: vary as a function of locomotor speed, so increase when running |
|
|
