Lippert ch.8 - Biomechanics pages 100-110
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| What are the 3 states of equilibrium? | stable, unstable, and neutral
[p100]
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| stable equilibrium | occurs when an object is in a position where disturbing it would require its Center Of Gravity (COG) to be raised
[p100]
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| example of stable equilibrium | a brick or a person lying flat on the floor
[p100]
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| unstable equilibrium | occurs when only a slight force is needed to disturb the object
[p100]
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| example of unstable equilibrium | balancing a pencil on its pointed end or a person standing on one leg
[p100]
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| neutral equilibrium | exists when an object's COG is neither raised nor lowered when it is disturbed
[p100]
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| example of neutral equilibrium | a ball rolling across the floor or a person moving across the room seated in a wheelchair
[p100]
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| What effect does lowering the COG have on an object? | the object will become more stable
[p100]
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| 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]
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| 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]
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| 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]
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| What effect does mass have on stability? | more mass = more stability
[p101]
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| What effect does friction have on a Base of Support (BOS)? | more friction = more stability
[p101]
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| 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]
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| 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]
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| What are machines used to change? | magnitude or direction of a force
[p102]
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| basic rule of all simple machines | the advantage gained in power is lost in distance
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| lever | rigid bar that can rotate around a fixed point when a force is applied to overcome resistance. Example: bone.
[p102]
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| axis | A fixed point around which a lever rotates. a.k.a. fulcrum
[p102]
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| force | causes the lever to move, usually muscular,
a.k.a. effort
[p102]
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| resistance | weight and/or pull that must be overcome for motion to occur
a.k.a. load
[p102]
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| force arm (FA) | distance between the force and the axis
[p103]
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| resistance arm (RA) | the distance between the resistance and the axis
[p103]
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| first class lever | Force _______Resistance
Axis
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| example of 1st class lever in human body | cervical flexion and hyperextension
[p104]
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| second class lever | Axis__Resistance__Force
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| example of 2nd class lever in human body | ankle plantar flexion
[p105]
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| third class lever | Axis__Force__Resistance
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| example of 3rd class lever | elbow flexion pertaining to the biceps
[p106]
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| Which type of lever favors speed and distance (ROM)? | 3rd class levers
[p106]
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| Which type of levers favor power? | 2nd class levers
[p106]
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| What type of lever is the brachioradialis normally during elbow flexion? | 2nd class lever
[p106]
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| Which type of lever will also favor speed and distance (ROM) when the axis is placed close to the force? | 1st class lever
[p103]
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| What type of lever is a wheelbarrow an example of? | 2nd class lever
[p104]
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| When does the biceps become a second class lever? | during elbow extension
[p107]
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| How does the brachioradialis become a 3rd class lever during elbow flexion? | when weight is added to the hand, thus changing the resistance
[p107]
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| 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]
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| fixed pulley | simple pulley attached to a beam, acting as a 1st class lever, only to change direction
[p108]
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| example of pulley in human body | the lateral malleolus of the fibula serves as a pulley for the peroneus longus
[p108]
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| 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]
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| mechanical advantage | number of times the machine multiplies the force
[p108]
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| wheel and axle | a wheel attached to and turning with an axle
[p109]
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| example of a wheel & axle in the human body | passive shoulder rotation
[p109]
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| 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]
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| inclined plane | flat surface that slants exchanging increased distance for less effort
[p110]
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| 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]
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