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biomechanics final*
chapters 10-14
| Question | Answer |
|---|---|
| statics | covers situations in which all forces acting on the body are balanced (in equilibrium) |
| dynamics | branch of biomechanics, dealing with bodies subject to unbalance |
| kinematics | branch of mechanics that considers the forces that produce or change motion |
| scalar quantities | single quantities (size or amount |
| vector quantities | double quantities (magnitude and direction) |
| relative motion- | the act or process of changing place or position with respect to some reference object |
| translatory motion | object is translated as a whole from one location to another |
| 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 |
| curvilinear motion- | refers to all curved translatory movement (moves in curved pathway) |
| angular/rotary motion- | when an object acting as a radius moves about a fixed point. |
| reciprocating motion | denotes repetitive motion |
| external factors modifying motion- | friction, air resistance, water resistance |
| 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 |
| speed equation= | distance/ time |
| velocity equation= | displacement/time |
| mean acceleration= | final velocity- initial velocity/ time |
| a= | v/t |
| v= | at |
| t= | v/a |
| factors that control the range of a projectile: | speed of release, angle of projection, and height of release |
| angular displacement equation= | C=2(pi)r |
| force- | that which pushes or pulls through direct mechanical contact or through the force of gravity to alter the motion of an object |
| what kind of quantity is force? | vector! |
| force possess both... | magnitude and direction! |
| internal forces- | muscle forces that act on various structures of the body |
| external forces- | outside the body (weight, gravity, air or water resistance, friction) |
| magnitude is directly affected by what? | muscle fibers |
| point of aplication | point at which force is applied to object |
| anatomical pulley- patella- | the patella increases angle of pull and increases rotary component |
| law of inertia- | body continues in its state of rest of uniform motion unless an unbalanced force acts upon it |
| law of acceleration- | F=mass x acceleration, acceleration is directly proportional to force causing it and inversely proportional to mass of object |
| impulse- | Ft= m(v-u) product of force and time is applied |
| momentum= | mass x velocity |
| 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 |
| 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 |
| 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 |
| conservation of momentum- | in any system where forces act on each other, the momentum is constant |
| What are the 6 forces that modify motion?? | 1) gravity 2) reaction forces 3) weight 4) friction 5) elasticity and rebound 6) fluid forces |
| what is friction? | the force that opposes efforts to slide or roll one body over another |
| friction is proportional to? | the force pressing two surfaces together |
| 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. |
| coefficient of elasticity- | e= the square root of bounce height/ drop height |
| 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 |
| a ball coming in with backspin hitting the floor has a | smaller angle of reflection |
| balls thrown with topspin will rebound from horizontal surfaces lower and with more horizontal velocity than that with which they struck the surface | true |
| balls hitting a horizontal surface with backspin rebound at | higher bounce and are slower |
| a ball with no spin will.. | develop some top spin on the rebound |
| a ball hitting with topspin will... | develop greater topspin when rebounding |
| laminar flow | if fluid around an object is smooth and unbroken |
| drag force | result of pressure on the leading edge of the object and the amount of backward pull produced by turbulence on trailing edge |
| Bernoulli's principle- | the pressure in a moving fluid decreases as the speed increases |
| 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 |
| torque- | the turning effect of an eccentric force, or moment of force |
| torque equation= | torque = force x moment arm (t=f x d) |
| moment arm- | the perpendicular distance between the force vector and the axis |
| force couple- | effect of equal parallel forces acting in opposite directions |
| 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. |
| 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 |
| fulcrum- | fixed point about which a lever turns when force applied |
| effort arm (EA)- | the perpendicular distance between the fulcrum and line of force of the effort |
| resistance arm (RA)- | the perpendicular distance between the fulcrum and the line of resistance force |
| first class levers- | axis lies between the effort and the resistance |
| mechanical advantage of first class levers- | balance |
| second class levers- | resistance lies between axis and effort; EA always longer than RA |
| advantage of second class levers- | magnifying the effects of effort so takes less force to move resistance |
| disadvantage of second class levers- | ROM sacrificed |
| third class levers- | effort leis between axis and resistance; Ra always longer of the two moment arms |
| 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. |
| 1st class lever abbreviation | EAR |
| 2nd class lever abbreviation | ARE |
| 3rd class lever abbreviation | AER |
| anatomical examples of first class lever- | head on neck, forearm when being extended by triceps against resistance |
| anatomical examples of second class lever- | calf muscles |
| non-anatomical examples of second class levers | wheel barrow, door handle, nutcracker |
| anatomical examples of third class lever | most muscles, biceps |
| non-anatomical third class lever- | screen door with spring closing |
| principle of levers equation= | E x EA = R x RA |
| mechanical advantage- | ability to magnify force |
| mechanical advantage (MA)= | resistance/ effort |
| MA also = | EA/RA |
| moment of inertia equation- | I = sum mr^2 |
| angular momentum= | moment of inertia x angular velocity (lw) |
| conservation of angular momentum- total angular momentum of a rotating body will remain constant unless | acted upon by external torques |
| a decrease in moment of inertia produces.. | an increase in angular velocity |
| what is center of gravity? | the balance point or the point about which a body would balance without tendency to rotate |
| location of center of gravity of human being in normal standing position varies with: | body build, age, and sex |
| females approximate COG (center of gravity)= | at 55% of standing height |
| male approx COG= | at 57% standing height |
| convert revolutions per second to radians per second | multiply rev/ sec x 360 then divide by 57.3 |
| convert radians per second to degrees per second | multiply by 57.3 |
Created by:
sbush0804
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