Torque Flashcards
Where is the force and load in a class 1 lever? Examples?
Both down on either side with fulcrum in the middle
seesaw - atalantoaxial joint
Where is the force and load in a class 2 lever? Examples?
fulcrum far left, load down in. middle, force up on right - standing on toes gastroc (wheelbarrow)
Where is the force and load in a class 3 lever? Examples?
fulcrum far left, force up in the middle, load down on the right
biceps brachi - elbow joint
what is torque? vetor or scalar?
vector the turnin geffect produce by a force
What are the 3 types of external forces,
centric, eccentric and force couples
What is a centric force? change in what type of motion?
external force directed trhy centre of gravity of an object - change in linear motion as per newtons 2nd law not angular
what is an eccentric force? What type of motion
for NOT directed thru centre of gravity - effect of force id change in linear AND angular morions of the object - Newtons 2nd law
What is a force couple? what type pf motion
paoir of non-colinear external forces equal but opposite in direction
- angular motion so the object rotates - net resultant foce is 0 so ther eis NO change in linear motion per Newtons first and 2nd law
Ehat is a moment (force or lever) arm defined as?
erpendicular (⟂) distance between the lineof action of a force and a parallel line passing through the axis of rotation
What is the torque if a centric force is applied
0
to find the moment arm what equation can you use
To find vertical component
sinangle = r/x
or fy/F
because
to fully cahracterize a torque one must decscribe what 3 things?
- the size of the torque
– the axis about which the turning effect is created
– the direction of the turning effect
How is driection of torque determined?
right hand thumb rule
Where is the line of action (pull for a muscle force)
Along the line between the tendons
The moment arm of. amsucle changes as the ___ changes
joint angle - max AT 90
When muscle force pulls at an angle, only the _____
component of force to the bone
(lever) produces torque; i.e. the ___ component
perpendiculat, rotary (vertical)
Wjat does the dislocating/stabilizing compenet do?
horizontal. - stablizes or dislococated joint
What are the 3 different types of compenents of muscular torque?
Rotary componentn (vertical), stabilizing component (to left), dislocating compenent (to right)
Can an object still have a net force of 0 if it is rotating?
yes - net force is only lienar otion
Can an onject be in static equillibirum if it rotating?
no external forces and torque must sum to 0
What is centre of gravity?
the point in a body around which its mass or weight is balanced and through which the force of gravity acts - where entire mass ot wieght is concentrated
where si CG in human body in anatomical position?
right in middle of waist
Cg of human bofy
left to right?
Back to front?
Top to bottom?
L to R = midline of bodu
Back to front. = thru shoulder and hips and just forward of ankle joints
Top to botoom - 55% standing height females
57% males
highr in infants and toddlers bc large head and short legs
Cg shifts in direction of ____
movement of a body part - depends on weught of body part and distance it moves
what is stability
the capacity fo an object to return to equillibrium or its original position after being displaced
What 3 things is stability affected by
height of CG - lower is better
size of base of - larger is better
Weight (heavier is better)
can direction of force impact stability?
YES
CG height is ____ as object si toppled Increase in CG height lead to increase in ___
raised, potential energy
The ____ the orgiinal ct height the ___ the increase in height
lower, greater hence PE is greater an d more work msut be done - lower cg id more stable
The most stable position for a person is one that maximizes ____
potential engery
is CG is ___ base of support the object will return to the original position after displacment which is called ___
below, stable equillibrium
If the CG is _____ the base of support, stability is only maintained if the line of gravity acting
on CG is _____
above, within the base of support
What is mechanical work (U) si unit?
product of force (F) and displacement (d) in the direction of that force - means by which energy si tranferred from one onject to another
joule (J)
to determine amount of work done on an obejct we need to knwo hat 3 things
average force of object, direction of force, displacment of obejct while force acts
What are three types of msucle contraciton and how does thsi impact work
isometric (statitc) = 0 work , concentric (shorterning) = pos, eccentric (lenghneing) = negative work
what is mechanical energy defined as?
The capacity to dow work also in J
what is total mecanical energy?
KE + PE
What is kinetic energy?
objects capacity to do wokr due to the motion of an object
What is potential energy?
Obejcts capcaity to do work due to position of object
Can energy be negative?
NO - only positive
In a closed system what happens to momentum? Is it same for KE?
It is conserved.Not same for KE as during impact some KEis onverted to other forms of energy like heat or sound
what are 2 types of PE?
gravitational potential energy and strain energy
what is gravitation PE?
PE due to an objects position relative to earth
Is gravity always psoitive in PE?
yes
What is strain energy?
Pe due to the deformation of an object liek pole vaulting - related to stiffness content K and deormation delta x
What is the work energy relationship?
work done by external forces acting on an object can change th eneergy of that objecy
to maximize increase in kinertic energy a ____ force needs to be applied over ____ distance?
large force over long distance
What is conservation of mechanical energy?
In absence fo external forces (other than gracity, no work is done and total mechanical energy is conserved (constant) Ei = Ef
What is concervation ofmechanical energy useful in?
motion of projectiles
- efore being dropped, an object has PE but no KE
– as it falls, PE decreases because height decreases but
KE increases because it accelerates due to gravity
– the decrease in PE is equal to the increase in KE
– the instant before the object strikes the ground, it has
no PE because height is zer
What is power?
rate of doing work in watts
What is naother definition of (linear) power?
product of average force and average
velocity
As the velocity of a contraction increases, the
maximal force the muscle can generate ___
decreases
true or false? the maximal force a muscle can generate is at the max velocity?
false?
____ msucle strength decreses with age?
isometric
what is peak effort reffered to? what type of contractipon does it measure
reffered to as maximal voluntary contraction (MVC) - isometric
How was angular velocity measured in the dorsifelxor experiement.
measured “isotonically”
− i.e., a fixed load is moved through a range of motion
as fast as possible
* loads normalized to peak torque duringsometric MV
When is max muscle power acheived
not at ffastest velocity or largest foce but a compromise between the two - usualy 1/3 of max velocity
As the duration of an activity increases, the power output which can be sustained ____
exponentially
decrease
