Ch.13 Flashcards
The angular equivalent of linear force is __, which may be thought of as rotary force.
torque
The product of a force and the perpendicular distance from the force’s line of action to the axis of rotation is know as __.
torque
What is the torque generated if a force of 12N is applied @ a perpendicular distance of 3m from an axis of rotation?
- 36 Nm
- multiply force (12N) by perp distance (3m)
What is the shortest perpendicular distance between a force’s line of action and the axis of rotation called?
- force arm
- lever arm
- moment arm
For any given muscle, the moment arm is the largest when the angle of pull on the bone it is attached to is closest to __.
90 degrees
The rotary effect created by an applied force is known as __, or moment of force.
torque
What is the formula for torque?
T=Fd⌄m
most human movement involves simultaneous tension development in __ __ __ muscle groups, the latter of which controls the velocity of the movement and enhances the stability of the joint at which the movement is occurring.
agonist and antagonist
In order to generate torque of 2.5Nm, what magnitude of force must be applied at a perp distance of .8m from the axis of rotation?
- 3.125 N
- 2.5Nm x .8m = 3.125N
The point of support, or axis, about which a lever may be made to rotate is known as a ___.
fulcrum
What does a force directed through an axis of rotation produce no torque?
because the force’s moment arm is 0
Within the human body, the __ for a muscle with respect to a joint center is the perp distance between the muscle’s line of action and the joint center.
moment arm
When net muscle torque and joint movement occur in the same direction
concentric torque
when net muscle torque occurs in the direction opposite joint motion
eccentric torque
what acts as a rigid bar?
bone
What serves as a fulcrum?
joint
What applies force?
muscle
Within the human body, the simultaneous action of agonist and antagonist muscle groups on opposite sides of a joint axis is analogous to the functioning of a ___ lever.
first-class
A lever positioned with the resistance between the applied load and the fulcrum is known as a ___.
second-class lever
a lever positioned with the applied force and the resistance on opposite sides of the axis of rotation is known as a __
first-class lever
a lever positioned with the applied force between the fulcrum and the resistance is known as a ___
third-class lever
Whenever the resistance arm of a lever is longer than the force arm, the __.
resistance may be moved through a relatively large distance
Most muscle-bone lever systems of the human body are the __ class for concentric contractions.
third
The mechanical effectiveness of a lever for moving a resistance
ratio of the moment arm of the force to the moment arm of the resistance
Most muscle-bone lever systems in the human body have a mechanical advantage of __
less than one
T/F: Whenever the moment arm of a force applied on a lever is greater than the moment arm of the resistance, the magnitude of the applied force needed to move a given resistance is more than the magnitude of the resistance.
False
What is the formula for the mechanical advantage of a lever?
moment arm (force)/moment arm (resistance)
In the human body, most muscle-bone lever systems are the __
third class
The angle of maximum mechanical advantage for any muscle is the angle at which the most __ can be produced
rotary force
The maximum mechanical advantages for the brachialis, biceps, and brachioradialis occur between angles at the elbow of approximately __
75 degrees and 90 degrees
A state characterized by balanced forces and torques is known as __
equilibrium
The arrangement of most third-class muscle-bone lever systems in the human body promotes __
range of motion and angular speed of the body segments
Bodies in motion are considered to be in a state of __ __ with all acting forces resulting in equal and oppositely directed inertial forces
dynamic equilibrium
What causes a bone to rotate around a joint center
rotary component
What pulls a bone away from a joint center
dislocating component
What pulls a bone toward a joint center
stabilizing component
The angle at the elbow at which maximum flexion torque is produced is approximately __, with torque capability progressively diminishing as the angle at the elbow changes in either direction.
80 degrees
In the context of Newtons first law of motion, what are the states of a body in equilibrium?
- motionless
- moving with constant velocity
__ refers to the concept indicating a balance between applied forces and inertial forces for a body in motion
D’Alembert’s principle
balance
a person’s ability to control equilibrium
base of support
area bound by the outermost regions of contact between a body and support surface or surfaces
center of mass/mass centroid/center of gravity
point around which the mass and weight of a body are balanced, no matter how the body is positioned
couple
pair of equal, oppositely directed forces that act on opposite sides of an axis of rotation to produce torque
dynamic equilibrium (D’Alembert’s principle)
concept indicating a balance between applied forces and inertial forces for a body in motion
1st class lever
lever position with the applied force and the resistance on opposite sides of the axis of rotation
fulcrum
the point of support, or axis, about which a lever may be made to rotate
lever
a simple machine consisting of a relatively rigid, bar-like body that may be made to rotate about an axis
mechanical advantage
ratio of force arm to resistance arm for a given lever
moment arm
shortest (perpendicular) distance between a force’s line of action and an axis of rotation
reaction board
specially constructed board for determining the center of gravity location of a body positioned on top of it
2nd class lever
lever positioned with the resistance between the applied force and the fulcrum
segmental method
procedure for determining total-body center of mass location based on the masses and center of mass locations of the individual body segments
stability
resistance of disruption of equilibrium
static equilibrium
motionless state characterized by
- ΣSFᵥ=0
- ΣSFₕ=0
- ΣSF=0
3rd class lever
lever positioned with the applied force between the fulcrum and the resistance
torque
the rotary effect of a force about an axis of rotation, measured as the product of the force and the perpendicular distance between the force’s line of action and the axis
