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Biomech. pg 100-110

Lippert ch.8 - Biomechanics pages 100-110

What are the 3 states of equilibrium? stable, unstable, and neutral [p100]
stable equilibrium occurs when an object is in a position where disturbing it would require its Center Of Gravity (COG) to be raised [p100]
example of stable equilibrium a brick or a person lying flat on the floor [p100]
unstable equilibrium occurs when only a slight force is needed to disturb the object [p100]
example of unstable equilibrium balancing a pencil on its pointed end or a person standing on one leg [p100]
neutral equilibrium exists when an object's COG is neither raised nor lowered when it is disturbed [p100]
example of neutral equilibrium a ball rolling across the floor or a person moving across the room seated in a wheelchair [p100]
What effect does lowering the COG have on an object? the object will become more stable [p100]
If an object's Line of Gravity (LOG) shifts beyond its Base of Support (BOS), what will happen to the object? the object will fall over [p101]
When a person leans to one side, their COG will move to that side. What can they do to help maintain their balance? raise their opposite arm or widen their stance [p101]
On a very windy day, how should a person stand to be the most stable? facing into the wind and placing one foot behind the other to widen their BOS in the direction of the wind [p101 & Figure 8-20]
What effect does mass have on stability? more mass = more stability [p101]
What effect does friction have on a Base of Support (BOS)? more friction = more stability [p101]
Why are patients on crutches encouraged to look down the hall instead of at their feet? Focusing on a stationary object will improve their balance as opposed to focusing on a moving object. [p101]
Name 4 simple machines and which are in the human body. lever, pulley, wheel and axle (in the human body) inclined plane (not in the body) [p102]
What are machines used to change? magnitude or direction of a force [p102]
basic rule of all simple machines the advantage gained in power is lost in distance
lever rigid bar that can rotate around a fixed point when a force is applied to overcome resistance. Example: bone. [p102]
axis A fixed point around which a lever rotates. a.k.a. fulcrum [p102]
force causes the lever to move, usually muscular, a.k.a. effort [p102]
resistance weight and/or pull that must be overcome for motion to occur a.k.a. load [p102]
force arm (FA) distance between the force and the axis [p103]
resistance arm (RA) the distance between the resistance and the axis [p103]
first class lever Force _______Resistance Axis
example of 1st class lever in human body cervical flexion and hyperextension [p104]
second class lever Axis__Resistance__Force
example of 2nd class lever in human body ankle plantar flexion [p105]
third class lever Axis__Force__Resistance
example of 3rd class lever elbow flexion pertaining to the biceps [p106]
Which type of lever favors speed and distance (ROM)? 3rd class levers [p106]
Which type of levers favor power? 2nd class levers [p106]
What type of lever is the brachioradialis normally during elbow flexion? 2nd class lever [p106]
Which type of lever will also favor speed and distance (ROM) when the axis is placed close to the force? 1st class lever [p103]
What type of lever is a wheelbarrow an example of? 2nd class lever [p104]
When does the biceps become a second class lever? during elbow extension [p107]
How does the brachioradialis become a 3rd class lever during elbow flexion? when weight is added to the hand, thus changing the resistance [p107]
pulley A grooved wheel that turns on an axle with a rope or cable riding in the groove. A pulley changes the direction or magnitude of a force. [p108]
fixed pulley simple pulley attached to a beam, acting as a 1st class lever, only to change direction [p108]
example of pulley in human body the lateral malleolus of the fibula serves as a pulley for the peroneus longus [p108]
movable pulley (not found in human body) the end of the rope is attache to a beam, the rope runs through a pulley to the other end where the force is applied, the load (resistance) is suspended from movable pulley [p108 & figure 8-34]
mechanical advantage number of times the machine multiplies the force [p108]
wheel and axle a wheel attached to and turning with an axle [p109]
example of a wheel & axle in the human body passive shoulder rotation [p109]
How does having a larger wheel change what happens at the axle? the larger wheel is essentially a longer Force Arm (FA), which needs less force to turn, but requires a longer distance [p109]
inclined plane flat surface that slants exchanging increased distance for less effort [p110]
general rule of rise over run for construction of a ramp 1 inch of rise for every 12 inches of run [last slide in ch 8 and mentioned in class]
Created by: jteich
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