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Biomech. pg 100-110
Lippert ch.8 - Biomechanics pages 100-110
| Question | Answer |
|---|---|
| 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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