1inertia; object will remain at rest unless force acts upon it. Example: pushing a shopping cart
Newton's First Law
2acceleration of an object is proportional to force applied. Example: force needed to throw a ball far vs short
Newton's Second Law
3for every action there is an equal and opposite reaction. Example: jumping from a hard surface compared to sand
Newton's Third Law
4constant force on earth, directionally downward
gravity
5what are some developmental implications of gravity
- Baby vs adult (Gravity is a good thing in development because it helps them get stronger, ex. Extending the neck)
- Reflexes
- Effect on muscle receptors and tone
- Vestibular equilibrium
6body’s natural balance point. Location: generally anterior to S2 vertebrae, positional changes
center of gravity COG
7body’s contact point with surface (if sitting your BOS would be your butt and two feet, if standing it would be your feet)
base of support BOS
8wider BOS = ___________ stable
more
9Lower COG = __________ stable
more
10increased mass = _________ stability
increased
11how do you define stability
COG and line of gravity within BOS
12external force that resists motion between two surfaces in contact. Examples: walking on ice vs carpet.
friction
13pushing together
compression
14pulled apart (can lead to dislocations
tension
15unaligned forces (usually the result of friction, the result of two parallel forces going opposite ways)
shear
16what is an example of shear
dragging a patient on a bed can damage their skin, rug burn
17twisting forces. Ex. Pulling and twisting someone’s arm. Not typically done in OT practice.
torsion
18two or more forces acting in same line. (push or pull in line). Examples: tug of war, calf muscles pull in same line to plantarflex.
linear forces
19what is best for joint mobilization
tension
20what is best for weightbearing
compression
21same plane, different line of action. Examples: abdominals and spine extensors produce trunk control, improperly boosting patient in bed
parallel forces
22____________ forces produce angular motion and shearing
parallel
23two equal and opposite forces, creates angular motion. Example: turning a wheel with one hand pushing, one pulling. Anatomical example: scapular muscles.
force couples
24rotary force causes rotational movement around an axis; force required from a muscle contraction to produce movement
torque
25angular force depends on two items
- force applied
- length of lever
26greater the force the more pressure applied to body part
force
27greater the mechanical advantage the less force applied to body part or less force required to complete task
mechanical advantage
28What are examples of levers used in your daily routine?
- Wrench
- Tweezers
- Wheelbarrow
- Bottle opener
- Jar opener
29Why are levers in the body important for function?
- Allows us to do things with better mechanical advantage.