[PT11] Mechanical Principles

force

that which alters the state of rest of a body or its uniform motion in a straight line

direction and magnitude of force

what is the composition of forces?

causes movement in the direction of the force

the effect of the application of a single force applied to a body

equivalent to a single force acting at a common point but with the magnitude equal to the sum of their forces

the effect of two forces acting in the same direction and at a common point

a state of equilibrium

the effects of two equal forces acting at a common point, and in opposite directions

movement in the direction of the greater force

the effect of two unequal forces acting at a common point and in opposite directions

their forces compound producing a desired effect

the effect of two forces acting at an angle to each other

rotation of the body

the effect of two unequal forces acting at different points and in opposite directions

tension

a system of forces tending to separate parts of the body with equal and opposite forces which hold the parts together; used synonymously with force

gravity

the force by which all bodies are attracted to the earth

force of gravity

acts continuously upon the human body, and if unopposed the body will fall to the ground

anti-gravity muscles

erect position is maintained by the integrated contraction of these muscles

center of gravity

the point through which the line of action of the weight acts

the body of the 2nd sacral vertebra

where the center of gravity of the human body is located

line of gravity

a vertical line through the center of gravity

the vertex of the skull, body of the 2nd sacral vertebra, and between the feet

where does the line of gravity of a human pass through?

base of support

the area by which a body is supported

the area between the feet

where is the base support in humans?

stable equilibrium

the body restore to its original position after being displaces

unstable equilibrium

the body tend to displace after application of a force, the body falls on the ground

neutral equilibrium

there is a displacement of the body but the height and position of the center of gravity remain (e.g. a ball moves on a flat surface)

in a lying position

when is the stability of a human greatest?

it becomes less stable as the center of gravity is raised and base of support is reduced

how does the human body become less stable?

kinetics

concentrates on the forces that produce or resist the movement

kinematics

deals with types of motion or movement without regard for the forces that produce motion (type, direction, and quantity of motion)

osteokinematics & arthrokinematics

subdivisions of kinematics

axis

a line about which movement takes place

plane

the surface which a movement takes place

axes & planes

these are used to describe movement

sagittal axis

in an anterior-posterior direction

frontal axis

in the side-to-side direction

vertical axis

is parallel to the line of gravity

horizontal plane

a surface that divides the body into upper and lower

frontal plane

a surface that divides body into anterior and posterior aspect

sagittal plane

a surface that divides the body into right and left

horizontal plane

which plane is trunk rotation performed?

frontal plane

which plane is shoulder adduction performed?

sagittal plane

which plane is shoulder flexion performed?

horizontal plane

which plane is supination-pronation performed?

frontal plane

which plane is hip abduction performed?

sagittal plane

which plane is elbow flexion performed?

sagittal plane

which plane is hip flexion performed?

speed

the rate at which the body moves

velocity

the rate of motion which incorporates direction

work

the product of force and distance

energy

the capacity of a body for doing work

potential energy

the capacity for doing work by virtue of position

kinetic energy

capacity for doing work because of its velocity

power

the rate of doing work or the rate of energy expenditure; (force*distance/time)

joules/second or ergs/second

the unit of power

acceleration

the rate of change in velocity

acceleration

increase in velocity

decceleration

decrease in velocity

momentum

the quantity of motion it possesses

mass x velocity

how do you calculate momentum?

inertia

the resistance of a body to any change in its state of rest or motion; Newton's first law of motion

friction

the force which opposes motion when one surface slides upon another

lever

a rigid bar which is capable of movement about a fixed point called fulcrum

when a force or effort (E) applied at one point in the lever, acts upon another force or weight (W) acting at a second point on the lever (F) - fulcrum

how is work done in a lever?

effort's arm

perpendicular distance from the fulcrum (F) to the effort (E)

weight's arm

perpendicular distance from the fulcrum (F) to the weight (W)

1st class lever

class of lever in which the fulcrum is in the middle of the weight and effort

2nd class lever

class of lever in which the weight is in the middle of the fulcrum and effort

3rd class lever

class of lever in which the effort is in the middle of the fulcrum and weight

example of 1st class lever

example of 2nd class lever

example of 3rd class lever

horizontal/transverse plane

a movement in the vertical axis would occur in which plane?

sagittal plane

a movement in the frontal axis would occur in which sagittal?

frontal plane

a movement in the sagittal axis would occur in which plane?

sagittal plane, frontal axis

which plane and axis does cervical forward flexion occur in?

horizontal/transverse plane, vertical axis

which plane and axis does internal rotation of the shoulder occur in?

horizontal/transverse plane, vertical axis

which plane and axis does circumduction occur in?

sagittal plane, frontal axis

which plane and axis does hip extension occur in?

frontal plane, sagittal axis

which plane and axis does neck lateral flexion occur in?