The study of mechanics as it relates to the functional and anatomical analysis of biological systems is called _______.
biomechanics
______ is the study of physical actions of forces.
Mechanics
______ and _____ are subcategories of mechanics.
Statics, dynamics
_____ involves the study of systems that are in a constant state of motion, whether at rest with no motion or moving at a constant velocity without acceleration.
Statics
_______ involves the study of systems in motion with acceleration.
Dynamics
In ____ , all forces acting on the body are in balance, resulting in the body being in equilibrium.
statics
For _______ , a system in acceleration is unbalanced due to unequal forces acting on the body.
dynamics
_____ is the study of spatial and timing characteristics of motion of the human body and its segments.
Kinematics
The variables used to describe motion are ______ , ______ , ______ , and _______.
time, displacement, velocity, and acceleration
Time, displacement, velocity and acceleration are variables used to describe both _____ and ____ motion (angular displacement, angular velocity, and angular acceleration).
linear, angular
The temporal characteristics of a performance, either of the totally skill or its phases.
Time
The length and direction of the path an athlete takes from start to finish.
Displacement
The direction of, and smallest angular change between, the rotating body's initial and final position.
Angular displacement
The displacement per unit of time.
Velocity
The angular displacement per unit of time.
Angular velocity
The rate of change of velocity.
Acceleration
The angular velocity per unit of time.
Angular acceleration
______ focuses on the various forces that produce a movement and the resulting motion.
Kinetics
______ forces are generated by muscles pulling via their tendons on bones, and to bone-on-bone forces exerted across joint surfaces.
Internal
______ forces are acting from outside (such as the force of gravity or the force from any body contact with the ground), environment, sport equipment, or opponent.
External
In general, internal forces _____ individual body segment movements, while external forces _____ body movements.
cause, affect
The musculoskeletal system may be thought of as a series of ______ used to increase ______.
simple machines... mechanical advantage
The ______ provided by machines enables us to apply a relatively small force, or effort, to move a much greater resistance or to move one point of an object a relatively small distance to result in a relatively large amount of movement of another point of
mechanical advantage
mechanical advantage can be determined by dividing ______ by _____.
the load, the effort
Machines function in 4 ways:
- Balance multiple forces
- Enhance force in an attempt to reduce total force needed to overcome a resistance
- Enhance range of motion & speed of movement so that resistance may be moved further or faster than applied force
- Alter resulting direction of
The musculoskeletal system provides for 3 types of machines in producing movement:
- Levers (most common)
- Wheel-axles
- Pulleys
Machine types not found in the body:
- Inclined plane
- Screw
- Wedge
Levers rotate about an axis as a result of force (or effort) being applied to cause its movement against a ______ or _____.
resistance, weight
In the body _____ represent the levers and the ____ represent the axes (fulcrums). ______ act to apply force.
bones... joints... Muscles
Three points determine type of lever & for which kind of motion it is best suited:
- Axis (or fulcrum)
- Point of force application
- Point of resistance application
Axis is between force and resistance in...
1st class levers
Resistance is between the axis and the force in...
2nd class levers
Force is between axis and resistance in...
3rd class levers
Force arm is commonly called _______.
moment arm
______ class lever is the only class of levers where we have a mechanical advantage in the body.
2nd
Maximal ability of a muscle to develop tension and exert force varies depending upon the _______ during contraction.
length of the muscle
Depending on the muscle involved, the greatest amount of tension can be developed when a muscle is stretched between _______ of its resting length.
100% to 130%
Depending on the muscle, stretch beyond 100% to 130% of resting length significantly ______ the amount of force muscle can exert.
decreases
A proportional decrease in ability to develop tension occurs as a muscle is _______.
shortened
When shortened to around ______ of its resting length, the muscle's ability to develop contractile tension is essentially reduced to zero.
50% to 60%
A _____ is the shortest perpendicular distance from the axis of rotation to the line of action of the force.
moment arm
______ is the measure of how much matter an object has.
Mass
_____ is the reluctance of an object to change its state of motion from rest to moving, to moving faster, or to slowing down back to rest.
Inertia
______ is influenced by the magnitude of moment arm and the magnitude of force.
Moment of force
_________ is a function of the mass of a rotating object and how its mass is distributed about its axis of rotation.
Moment of inertia
The center of mass is located at the _______ of the body; a point found in or about a body where the mass could be concentrated.
balance point
_____ is the measure of amount of matter an object has as well as inertia.
Mass
_____ is the measure of the force of gravity.
Weight
_____ is the same no matter where you are. ______ varies directly with the magnitude of the acceleration due to gravity.
Mass... Weight
Moment of force =
Moment arm x Force
_____ is the turning effect of an eccentric force.
Torque
_______ is force applied off center or in a direction not in line with the center of rotation of an object with a fixed axis.
Eccentric force
In objects without a _______ , eccentric force is an applied force that is not in line with the object's center of gravity.
fixed axis
For _____ blank to occur, an eccentric force must be applied.
rotation
In humans, contracting muscle applies an _____ to bone upon which it attaches and causes the bone to rotate about an axis at the joint.
eccentric force
Torque =
Force x Moment arem
______ is the perpendicular distance between the location of force application and the axis.
Moment arm (or force arm)
The greater the distance of the force arm, the more ______ produced by the force.
torque
Often, we purposely ______ moment arm length in order to _______ torque so that we can more easily move a relatively large resistance (increasing ________).
increase... increase... leverage
________ is the distance between the axis and the point of resistance application.
Resistance arm
if either of the resistance components increase, there must be an increase in one or both of the ________.
force components
Greater resistance or resistance arm requires greater force or longer ________.
moment arm
Greater force or moment arm allows a greater amount of resistance to be moved or a _________ to be used.
longer resistance arm
In _______ levers, if the force arm and resistance arm are equal in length, a force equal to the resistance is required to balance it.
1st class
In ______ levers, as the force arm becomes longer, a decreasing amount of force is required to move a relatively larger resistance.
1st class
in _______ levers, as the force arm becomes shorter, an increasing amount of force is required to move a relatively smaller resistance.
1st class
In ______ levers, moving the resistance closer to the axis increases the mechanical advantage, but decreases the distance that the resistance is moved.
2nd class
In ______ levers, the closer the resistance is positioned to the point of force application, the less mechanical advantage, but the greater the distance is moved.
2nd class
In ______ levers, a force greater than the resistance, regardless of the point of force application, is required due to the resistance arm always being longer.
3rd class
In ______ levers, moving the point of force application closer to the axis increases the range of motion and speed.
3rd class
In ______ levers, moving the point of force application closer to the resistance decreases the force needed.
3rd class
The longer the lever, the more effective it is in imparting _______.
velocity
Longer levers produce more ______ and thus better performance in some sports such as baseball, hockey, golf, field hockey, etc.
linear
For quicker movements, it is desirable to have a _____ lever arm.
shorter
Single ______ function to change effective direction of force application (Mechanical advantage = 1)
Pulleys
Pulleys may be combined to form _________ to increase mechanical advantage.
compound pulleys
________ is: resistance created at the interface of two bodies in contact with one another and acting in a direction that is opposite impending or actual movement.
Friction
Microscopic irregularities on opposing surfaces (or rough edges) lead to objects _______ to each other (think velcro).
adhering
______ is the amount of friction between two objects that have not yet begun to move.
Static friction
________ is friction occurring between two objects that are sliding upon one another.
Kinetic friction
Static friction is always ______ than kinetic friction.
greater
It is always more difficult to _______ dragging an object across a surface than to _______ dragging.
initiate... continue
________ is the ratio between force needed to overcome the friction over the force holding the surfaces together.
Coefficient of friction
_________ is theprocess whereby the body's state of equilibrium is controlled for a given purpose.
Balance
During balance, the bas of ________ and the location of the _______ is manipulated.
support... center of mass (COM)
If the line of gravity passes through some part of the body's __________ , the body will be balanced.
base of support (BoS)
________ is a measure of the difficulty with which equilibrium can be disturbed.
Stability
To increase static equilibrium:
- Increase the base of support (BoS).
- Increase the inertia of the body (i.e. increase the mass).
- Decrease the vertical distance between the COM and the BoS (i.e. lower the COM).
- Increase the distance between the point where a vertical line from the
Any external force that acts ________ the body's COM will create a moment of force acting on the total body.
away from
Usually, the off-center force is a ________ from the ground or equipment, resulting from the internal muscle forces generated by the athlete.
reaction force
If an athlete has forward momentum and a ________ is created, then some or all of the linear motion can be transferred into angular motion.
pivot point
Maximal ability of a muscle to develop tension and exert force varies depending upon the _______ during contraction.
length of the muscle