Chapter 8- Anatomy and Kinesiology

Law of Inertia

Object at rest tends to stay at rest, an object in motion tends to stay in motion

A _____ is needed to overcome the inertia of an object and cause it to move, stop or change direction

Force

Acceleration

Any change to the velocity of an object

Mass

amount of matter in an object

Law of Acceleration

Amount of acceleration depends on the strength of the force applied to the object

Acceleration is _______ _________ to the mass of an object

inversely proportional

Law of Action

For every action, there is an equal but opposite reaction

Force

When an object acts on another object.
Can be a push or pull
Movement occurs when one force overcomes another
Forces are vector quantities

Linear force

Two or more forces are acting along the same line (Two guys pulling a boat to shore)

Parallel force

Forces in the same plane and in the same OR opposite direction. (Back brace)

Concurrent force

Two or more forces acting on a common point, pushing or pulling in different directions. The overall effect of this is known as the resultant force.

Force couple

When two or more forces act in different directions, creating a turning effect (happens with the scapula during shoulder abduction)

Moment of force

the ability to produce rotation around an axis

Torque depends on what two factors?

- amount of force exerted
- distance the force is from the axis

(Wrench)

Torque is highest at what angle?

90 degrees

Stability

When all torques are even and in a state of equilibrium

Center of Gravity

Balance point of an object; located about the level of the S2 vertebrae

Base of Support (BOS)

Part of body in contact with the supporting surface

Line of Gravity

Vertical line passing through the COG toward the earth

First class lever

Axis is located between the force and resistance

Second class lever

Resistance is in the middle, with axis and force opposite

Third class levers

Force in middle, with resistance and axis opposite ends

How does elbow flexion change classes of levers

Biceps is a 3rd class lever. Eccentric action moves force to gravity and resistance to biceps, to second class lever.

Wheel and axle

Type of lever, large wheel attached to smaller wheel used to increase force exerted. (Shoulder rotation, No money's/Ws, Internal/External rotation)

Ramps

The longer a ramp is, the less force needed to move up a level