1 & 8: Basic Info and Basic Biomechanics

Question 1

What are the 5 segments of the body and their parts?

Answer 1

1. Head
2. NecK
3. Trunk (thorax and abdomen)
4. UE (arm, forearm, hand)
5. LE (thigh, leg, foot)

Question 2

What is LINEAR/TRANSLATORY motion?

Answer 2

Occurs in a more or less straight line from one location to another; all parts of the object move the same distance, in the same direction, and at the same time

Question 3

What is RECTILINEAR motion?

Answer 3

Movement that occurs in a straight line, like a child sledding down a hill

Question 4

What is CURVILINEAR motion?

Answer 4

Movement occurs in a curved path that is not necessarily circular, such as the path a skier takes coming down a ski slope

Question 5

What is ANGULAR/ROTARY motion?

Answer 5

All parts of the object move through the same angle, in the same direction, and at the same time, but they do not move the same distance

• Most movement in the body is ANGULAR and outside the body is LINEAR!
• Ex. when a person flexes their knee, the joint serves as the axis of rotation and the foot travels farther through space than does the ankle or leg

Question 6

What is OSTEOKINEMATICS?

Answer 6

The relationship of the movement of bones around a joint axis

• Ex. humerus moving on scapula

Question 7

What is ARTHROKINEMATIC motion?

Answer 7

The relationship of joint surface movement (spin, glide, roll)

Question 8

What is the difference between “kinetics” and “kinematics”?

Answer 8

KINETICS deals with forces causing movement in a system, and KINEMATICS describes the movement created by the force which involves the time, space, and mass aspects of a moving system.

Question 9

What is FORCE and VECTOR?

Answer 9

A push or pull action that can be represented by a vector (quantity having both magnitude and direction)

• Ex.: If you push a wheelchair, you would push it with a certain speed and in a certain direction

Question 10

What is VELOCITY?

Answer 10

A vector that describes speed and is measured in units such as feet per second or miles per hour

Question 11

What is SCALAR and MASS?

Answer 11

SCALAR quantity describes only magnitude (length, area, volume, and mass), and MASS refers to the amount of matter that a body contains

Question 12

What is INERTIA?

Answer 12

The property of matter that causes it to resist any change of its motion in either speed or direction

Question 13

What is TORQUE?

Answer 13

The tendency of force to produce rotation around an axis

Question 14

What is FRICTION?

Answer 14

A force developed by two surfaces, which tends to prevent motion of one surface across another

Question 15

What is Newton’s Law of Inertia?

Answer 15

An object at rest tends to stay at rest, and an object in motion tends to stay in motion

• Ex. if you get in a car accident without a seatbelt on, you will continue to go through the windshield even though the car has stopped

Question 16

What is Newton’s Law of Acceleration?

Answer 16

The amount of acceleration of an object depends on the force; force is also required to change the direction of the object; acceleration is produced when a force acts on a mass.

• The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object).
• Bigger mass, bigger push!

Question 17

What is Newton’s Law of Reaction?

Answer 17

For every action, there is an equal and opposite reaction

• The strength of the reaction is always equal to the strength of the action, and it occurs in the opposite direction

Question 18

LINEAR FORCE

Answer 18

2 or more forces acting along the same line (ex. 2 people pulling a boat with the same rope in the same direction)

Question 19

PARALLEL FORCE

Answer 19

Occur in the same plane in the same or opposite direction (i.e., brace)

Question 20

CONCURRENT FORCE

Answer 20

2 or more forces push or pull in different directions; the resultant force is produced

• 2 forces from different angles change the trajectory of the force
• Ex. pushing a chair forwards and sideways will move the chair diagonally
• Ex. throwing a kickball (pushing from the shoulder and pulling from the elbow)

Question 21

FORCE COUPLE

Answer 21

Occurs when two or more forces act in different directions, resulting in a turning effect (ex. scapular rotation due to combined forces of upper and lower traps and serratus anterior)

Question 22

TORQUE

Answer 22

Also called “moment of force”; the ability of force to produce rotation around an axis

Influence torque by

1. Increase force
2. Increase length of handle/club

Torque is the amount of muscle contraction (force) that is required to produce rotary joint motion

Question 23

MOMENT ARM

aka TORQUE ARM

Answer 23

Perpendicular to the line of pull & center of the joint; if force is directed through the joint axis, no torque is produced (greatest when the angle of pull is at 90 degrees)

Question 24

STABILIZING FORCE

Answer 24

Generated when the moment arm is shorter (not letting it move)

Question 25

ANGULAR FORCE

Answer 25

Most of the force generated by the muscle is directed at rotating, not stabilizing, the joint (generated when the moment arm is longer)

Question 26

DISLOCATING FORCE

Answer 26

Force is being directed away from the joint

• As the range of motion moves farther away from 90 degrees, stabilizing force is translated to dislocating force

Question 27

What is STABILITY?

Answer 27

A state of equilibrium that occurs when an object is balanced; all forces are equal

• Dependent on Center of Gravity (COG) and Base of Support (BOS)
• COG in adult= belly button; child= chest

Question 28

GRAVITY

Answer 28

The force of attraction by which terrestrial bodies tend to fall toward the center of the earth (gravitational force is directed downward, toward Earth’s center)

Question 29

Center of Gravity (COG)

Answer 29

Balance point where all forces acting on the object are equal

Question 30

Base of Support (BOS)

Answer 30

Contact points of the body to the supporting surface

Question 31

Line of Gravity (LOG)

Answer 31

An imaginary line passing vertically through the body, towards the center of the earth

Question 32

True or False?
The lower the COG, the more stable an object

Answer 32

True: a higher COG becomes less stable, so a lower COG is most stable

Question 33

What is a LEVER?

Answer 33

Rigid; can rotate around a fixed point (axis or fulcrum) when force is applied.

• Force or effort causes the lever to move
• Levers are influenced by shortening or lengthening the lever arms: carry a 5 lb weight 20’ with 90º shoulder flexion (long lever arm); then with the shoulder at neutral and 90º elbow flexion (shorter lever arm)

Question 34

What are the 3 classes of levers?

Answer 34

1. Axis/Fulcrum- the fixed point around which the lever rotates
2. Force/Effort- causes the lever to move (usually muscular)
3. Resistance/Load- must be overcome for a motion to occur can include the weight of the part of the body being moved, the pull of gravity on the part, or an external weight being moved by the body part

Question 35

What is the FORCE ARM?

Answer 35

Distance between the force and the axis

Question 36

What is the RESISTANCE ARM?

Answer 36

The distance between the resistance and the action

Question 37

What is a PULLEY?

Answer 37

Consists of a grooved wheel that runs on an axle with a rope or cable riding in the groove (purpose is to change the direction of a force or to increase or decrease its magnitude)

Question 38

What is a FIXED PULLEY?

Answer 38

A simple pulley attached to a beam; acts as a FIRST CLASS LEVER (used only to change direction)

• Fixed pulleys in the human body change the direction of a muscle’s force

Question 39

What are a WHEEL and AXLE?

Answer 39

Wheel or crank, attached to and turning together with an axle

• The larger the wheel in relation to the axle, the easier it is to turn the object
• In the human body, the shoulder serves as the axle, and the forearm serves as the wheel
• With the elbow flexed, the wheel(forearm) is much longer than the axle(shoulder joint) and thus much easier to turn