Biomechanics

Question 1

Newton’s 1st Law

Answer 1

The Law of Inertia

A body at rest will stay at rest, unless acted on by an external force…

A body in motion maintains a constant velocity unless acted on by a force.

No net force = no change in motion.

Question 2

Newton’s 2nd Law

Answer 2

The Law of Acceleration

The acceleration of an object is proportional to the net force applied.

The net force = the vector sum of all the external forces

Question 3

Newton’s 3rd Law

Answer 3

The Law of Action-Reaction

If a force is applied to body #1 on body #2, then an equal and opposite force is applied by body #2 on body #2 (for every action there is an equal and opposite reaction)

Question 4

Weight

Answer 4

Mass x Gravity (9.8m/s^2)

Question 5

Force

Answer 5

Any interaction which tends to change the motion of an object

Question 6

Torque

Answer 6

Force x Moment Arm

Question 7

Moment Arm

Answer 7

Perpendicular distance from pivot point to line of action (weight)

Question 8

Vector

Answer 8

has magnitude and direction

Question 9

Class I Lever (Mechanical Advantage)

Answer 9

Variable depending on distances from axis points

Question 10

Class II Lever (Mechanical Advantage)

Answer 10

Force of the muscle has the mechanical advantage

Question 11

Class III Lever (Mechanical Advantage)

Answer 11

Weight/resistance has the mechanical advantage

Question 12

Mechanical advantage

Answer 12

MA = Force arm/ resistance arm

Question 13

Rotary Component (Y Axis)

Answer 13

perpendicular to the long axis of Bone

Clockwise (-Y)
Counterclockwise (+Y)

Question 14

Translatory Component (X-Axis)

Answer 14

parallel to long axis of bone

-Compression or distraction

Question 15

Anatomic Pulleys

Answer 15

1. Changes direction of pull
2. Moves muscle away from axis of rotation to increase mechanical advantage (increase moment arm)

Lack of anatomic pulley compromises the muscles ability to produce torque on a body segment