Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
34 Cards in this Set
- Front
- Back
|
two main areas of mechanics
|
statics (nonmoving systems)
dynamics (moving systems) |
|
|
force
|
push or pull action
|
|
|
vector
|
quantity having both magnitude and direction
|
|
|
inertia
|
property of matter that causes it to resist any change of motion
|
|
|
Torque
|
force to produce rotation
|
|
|
friction
|
developed by motion of two surfaces
|
|
|
velocity
|
speed
|
|
|
Newton's Three Laws of Motion
|
1. Law of inertia - object will stay at rest or in motion until a force overcomes it
2. Law of acceleration - the amount of acceleration depends of strength of force 3. Law of action/reaction - for every action there is an equal and opposite reaction |
|
|
Linear external force
|
two or more actions along the same line. Normal forces are compressive and tensile. Shear force causes more damage than normal forces (rug burn)
|
|
|
Parallel external forces
|
forces that occur in the same plane, in the same or opposite direction
|
|
|
Concurrent external forces
|
two more more forces act from a common point, but pull in different directions, yielding the net effect of resultant force
|
|
|
external force couple
|
two forces act in equal but opposite direction, giving turning effect (opening jar)
|
|
|
Muscle torque is greatest when movement arm is at what position
|
90 degrees
|
|
|
What determines a muscle forces' magnitude?
|
The number of active muscle fibers
|
|
|
What produces stability of an object?
|
When all torques acting on it are even
|
|
|
How is the center of gravity determined?
|
The position and relation to the earth
|
|
|
Base of support
|
The part of the body that is in contact with the supporting surface
|
|
|
Line of gravity
|
Imaginary vertical lien passing down through the COG toward center of the earth - should be in the middle of the BOS for greatest stability
|
|
|
4 things that give greater stability
|
1. Wider BOS
2. Greater mass 3. greater friction 4. when moving, focusing on stationary object rather than looking down at feet |
|
|
Lever
|
rigid bar that can rotate about a fixed point when a force is applied to overcome resistance
|
|
|
Fixed point about which a lever can rotate
|
Axis or fulcrum
|
|
|
Force
|
What causes a lever to move, usually muscles
|
|
|
Resistance
|
What must be overcome for motion to occur - includes weight of object being moved, gravity, external weight
|
|
|
Three types of levers
|
1. First Class
2. Second Class 3. Third class |
|
|
First class lever
|
F___________R
A Designed for balance: head sitting on C1 |
|
|
Second Class Lever
|
R_____________F
A best used for power: wheelbarrow, standing on tip toes |
|
|
Third Class Lever
|
___________F R
A Best for ROM - speed and distance. Most common in body, example is elbow flexion |
|
|
A shortened resistance arm requires more/less force (carrying something close to your body)
|
less
|
|
|
More/less force is required when resistance is as close to axis as possible
|
less
|
|
|
2-joint muscles in which it's possible to obtain active and passive insufficiency
|
1. Triceps
2. Biceps 3. Hamstring 4. Quads 5. Wrist flexors and extensors 6. Extrinsic finger flexors and extensors |
|
|
Open Kinetic Chain
|
Isotonic Movement or exercise in which the origin is fixed and the insertion moves. Occurs in every ROM
|
|
|
Closed Kinetic chain
|
Movement or exercise in which the origin is fixed and the insertion moves, such as pullups and pushups, situps, etc.
|
|
|
Closed packed joint position
|
Joints push together, such as standing, runnign squat
|
|
|
Open packed joint position
|
Where joints are pulled apart, such as leg lift
|
