EXSC 350 Chap 5 Flashcards
Torque (T) =
Fr
Force x moment arm (perpendicular distance)
What is a Torque?
A moment of Force
A rotary effect created by an applied force
It is the ANGULAR EQUIVALENT of LINEAR force
Greater T results in a ______ tendency for rotation to occur and a ______ angular acceleration.
Greater
Greater
Moment Arm is _______ and ______ distance between a force’s line of action and axis of rotation
Perpendicular and shortest
Any perpendicular will chance the moment arm ______
Length
A Force Couple is a pair of equal and opposite forces that produce T in the _____ direction.
Same
Equal magnitude
Ex: cycling, steering wheel
Tendon
Muscle to bone
Ligament
Bone to bone
Joint torques
Produce movement of body segments.
Antagonistic and Agonistic muscles working change in joint position = net T
Joint torque direct measure example:
Place a strain gauge in the muscle
Joint torque indirect example:
EMG
Isokinetic device
1st Class Lever
Ex: neck (atlanto-occipital joint), triceps, see-saw
E F R
*Least common
2nd Class Lever
Ex: Calf (MTP joint), wheelbarrow
F R E
3rd Class Lever
Ex: Biceps, broom
F E* R
*Most Common in body
Mech Adv. Resistance
Purpose of levers
To gain mechanical advantage
To gain a greater ROM with sm force arm movement
Mechanical Adv. Formula
Force/Resistance
> 1 Gain Mech adv.
<1 Lose Mech adv.
=1 No Mech adv.
Rotary Component
The only force component that will cause the bone to rotate about the joint center. Perpendicular to the bone. (Y component)
Dislocating Component
The components of force that is parallel to the bone pulling the bone AWAYSATURDAY form the joint center.
(X component)
Stabilizing Component
The component of force that is parallel to the bone pulling the bone TOWARD the joint center.
(X component)
If the Angle is < 90 deg…..
Rotary and Dislocating components (y,x)
If an Angle is > 90 deg…
Has both Rotary and Stabilizing components (y,x)
If an Angle is at 90 deg….
It has 100% Rotary component
Biceps produce the most force at what angle of a curl?
~80 deg
The force generated (strength) is highest
The specific angles in which the muscle is stronger/stable __________ from person to person.
Varies
Angles are in reference to the ______ compared to the bone not _____ compared to ______.
MUSCLES
Bone to Bone
The _____ of the muscle determine the force generated.
Length
Static Equilibrium
Condition when a body is completely motionless.
Implying force but no mvmt = isometric contraction
Net Vector Sum = Zero
COG (Center of Gravity)
Point about which the body mass or weight is equally distributed and through which the force of gravity acts.
Important for Stability and Balance
Mechanically, a body behaves as if all of its mass is concentrated at the __________________.
COG
When analyzing the human body’s weight as a force for mechanical analyses, the vector representing that force is drawn through the body’s ___________.
COG
Stability
Resistance to linear and/or angular acceleration
Balance
Ability to control equilibrium
(Improving Stability)
_______ body mass.
Increase ________ b/t body and contact surface
Increase
Friction
(Improving Stability)
Increase _____ of support base in direction of ____ __ ____ of external force.
_________ position COG near edge of support base on the side of the oncoming external force
Friction; Line of action
Horizontally
(Improving Stability)
If no external force, the you want your COG in the ______ of your support base.
Vertically positioning COG as _____ as possible
Middle
Low
