chapters 10-14
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| statics | covers situations in which all forces acting on the body are balanced (in equilibrium)
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| dynamics | branch of biomechanics, dealing with bodies subject to unbalance
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| kinematics | branch of mechanics that considers the forces that produce or change motion
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| scalar quantities | single quantities (size or amount
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| vector quantities | double quantities (magnitude and direction)
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| relative motion- | the act or process of changing place or position with respect to some reference object
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| translatory motion | object is translated as a whole from one location to another
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| rectilinear motion- | the straight-line progression of an object as a whole with all its parts moving the same distance in the same direction at a uniform rate of speed
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| curvilinear motion- | refers to all curved translatory movement (moves in curved pathway)
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| angular/rotary motion- | when an object acting as a radius moves about a fixed point.
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| reciprocating motion | denotes repetitive motion
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| external factors modifying motion- | friction, air resistance, water resistance
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| internal/ anatomical factors modifying motion- | friction in joints, tension of antagonists. ligaments and fascia, anomalies of bone and joint structure, atmospheric pressure inside joints, presence of interfering soft tissues
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| speed equation= | distance/ time
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| velocity equation= | displacement/time
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| mean acceleration= | final velocity- initial velocity/ time
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| a= | v/t
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| v= | at
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| t= | v/a
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| factors that control the range of a projectile: | speed of release, angle of projection, and height of release
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| angular displacement equation= | C=2(pi)r
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| force- | that which pushes or pulls through direct mechanical contact or through the force of gravity to alter the motion of an object
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| what kind of quantity is force? | vector!
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| force possess both... | magnitude and direction!
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| internal forces- | muscle forces that act on various structures of the body
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| external forces- | outside the body (weight, gravity, air or water resistance, friction)
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| magnitude is directly affected by what? | muscle fibers
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| point of aplication | point at which force is applied to object
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| anatomical pulley- patella- | the patella increases angle of pull and increases rotary component
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| law of inertia- | body continues in its state of rest of uniform motion unless an unbalanced force acts upon it
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| law of acceleration- | F=mass x acceleration, acceleration is directly proportional to force causing it and inversely proportional to mass of object
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| impulse- | Ft= m(v-u) product of force and time is applied
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| momentum= | mass x velocity
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| What are linear forces? give an example. | forces applied in same direction along the same action line ex) gastrocs and soleus acting at ankle joint, psoas and iliacus acting at hip joint
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| What are concurrent forces? give an example. | forces acting at the same point of application but at different angles. ex) several fball players blocking each other in blocking situation
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| What are parallel forces? give example. | forces are not in the same line but parallel to each other act at different points on body ex) holding a 10 N weight in hand with arm flexed at 90 degrees
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| conservation of momentum- | in any system where forces act on each other, the momentum is constant
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| What are the 6 forces that modify motion?? | 1) gravity 2) reaction forces 3) weight 4) friction 5) elasticity and rebound 6) fluid forces
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| what is friction? | the force that opposes efforts to slide or roll one body over another
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| friction is proportional to? | the force pressing two surfaces together
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| what is elasticity? | the ability of an object to resist distorting influences and to return to its original size and shape when the distorting forces are removed.
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| coefficient of elasticity- | e= the square root of bounce height/ drop height
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| The size of the rebound angle compared with that of the striking angle depends on | the elasticity of the striking object and the friction between the two surfaces
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| a ball coming in with backspin hitting the floor has a | smaller angle of reflection
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| balls thrown with topspin will rebound from horizontal surfaces lower and with more horizontal velocity than that with which they struck the surface | true
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| balls hitting a horizontal surface with backspin rebound at | higher bounce and are slower
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| a ball with no spin will.. | develop some top spin on the rebound
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| a ball hitting with topspin will... | develop greater topspin when rebounding
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| laminar flow | if fluid around an object is smooth and unbroken
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| drag force | result of pressure on the leading edge of the object and the amount of backward pull produced by turbulence on trailing edge
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| Bernoulli's principle- | the pressure in a moving fluid decreases as the speed increases
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| eccentric force- | a force whose direction is not in line with the center of gravity of a freely moving object or the center of rotation of an object with a fixed axis of rotation
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| torque- | the turning effect of an eccentric force, or moment of force
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| torque equation= | torque = force x moment arm (t=f x d)
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| moment arm- | the perpendicular distance between the force vector and the axis
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| force couple- | effect of equal parallel forces acting in opposite directions
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| principles of torques- | resultant torques of a force system must be equal to the sum of the torques of the individual forces of the system about the same point.
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| What is a lever? | a simple machine that operates according to the principle of torques; a rigid bar that can rotate about a fixed point when force applied to overcome resistance
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| fulcrum- | fixed point about which a lever turns when force applied
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| effort arm (EA)- | the perpendicular distance between the fulcrum and line of force of the effort
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| resistance arm (RA)- | the perpendicular distance between the fulcrum and the line of resistance force
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| first class levers- | axis lies between the effort and the resistance
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| mechanical advantage of first class levers- | balance
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| second class levers- | resistance lies between axis and effort; EA always longer than RA
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| advantage of second class levers- | magnifying the effects of effort so takes less force to move resistance
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| disadvantage of second class levers- | ROM sacrificed
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| third class levers- | effort leis between axis and resistance; Ra always longer of the two moment arms
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| principle of levers- | a lever of any class will balance when the product of the effort and the effort arm equals the product of the resistance and the resistance arm.
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| 1st class lever abbreviation | EAR
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| 2nd class lever abbreviation | ARE
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| 3rd class lever abbreviation | AER
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| anatomical examples of first class lever- | head on neck, forearm when being extended by triceps against resistance
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| anatomical examples of second class lever- | calf muscles
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| non-anatomical examples of second class levers | wheel barrow, door handle, nutcracker
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| anatomical examples of third class lever | most muscles, biceps
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| non-anatomical third class lever- | screen door with spring closing
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| principle of levers equation= | E x EA = R x RA
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| mechanical advantage- | ability to magnify force
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| mechanical advantage (MA)= | resistance/ effort
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| MA also = | EA/RA
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| moment of inertia equation- | I = sum mr^2
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| angular momentum= | moment of inertia x angular velocity (lw)
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| conservation of angular momentum- total angular momentum of a rotating body will remain constant unless | acted upon by external torques
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| a decrease in moment of inertia produces.. | an increase in angular velocity
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| what is center of gravity? | the balance point or the point about which a body would balance without tendency to rotate
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| location of center of gravity of human being in normal standing position varies with: | body build, age, and sex
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| females approximate COG (center of gravity)= | at 55% of standing height
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| male approx COG= | at 57% standing height
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| convert revolutions per second to radians per second | multiply rev/ sec x 360 then divide by 57.3
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| convert radians per second to degrees per second | multiply by 57.3
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