Torque (Test 2) Flashcards
What is torque
The turning effect about an axis created by a force (eccentric). expressed in Nm, and is a vector quantity.
( T = Fr )
What is r
the perpendicular distance between the axis of rotation and the line of force.
which torque is positive, which is negative (clockwise vs. counterclockwise)
Clockwise is negative
counterclockwise is positive
What conditions must be met for there to be static equilibrium
∑ F = 0, ∑ T = 0.
What is the center of mass? (or center of gravity)
The theoretical location at which the entire mass of the body seems to concentrated or centered, the resultant force of gravity seems to be acting upon this point.
Where mass on both sides of the point is equal
where is the center of mass in the human body
just behind the bellybutton
Why is center of mass important
- because it greatly affects performance
2. because it greatly affects stability
What affects stability
- height of the center of mass
2. the horizontal position of center of mass relative to the base of support
what is the equation used to find whole body center of mass
Σ(W×r) = (ΣW) × r CM
What is mechanical advantage
a ratio of perpendicular distances ( r ), internal vs. external. ri/re.
do humans have high or low mechanical advantages. What does that mean?
Low
that means that they lose strength, but they gain flexibility and increase movement.
What is an eccentric force
a force that is not directed at the joint axis. Causes rotation
What is a concentric force
a force that is directed directly at the joint axis. Doesn’t cause rotation.
What are the two components of a torque
- Fr, rotary compoment
2. Fc, compressive component
What is the purpose of the patella
It allows for more knee extension torque because it increases the angle of insertion by the muscle, which increases the rotary component of muscle force
What is the compressive component of muscle force and why is it important
it’s the component that is directed at the axis of rotation
It’s important because it stabilizes the joint
What is the rotary component of muscle force and why is it important
It’s the component of muscle force that is perpendicular to the compressive component of muscle force.
It’s important because it causes rotation.
What happens to the rotary component of muscle force as joint angle decreases
it decreases too.
What are the steps to quantify center of mass
- Take pictures
- Quantify/Digitize joint locations
- calculate segmental center of mass
- establish an origin
- calculate each segments torque
- sum up torque relative to the origin
- divide the sum of torque by the whole body mass
