Biomechanics Pt. 3 (9/5d)

Question 1

For every force, there is an ___ and ___ force

Answer 1

equal and opposite

Question 2

Vector Composition

Answer 2

Adding forces

Vector L + Vector M = Vector R (resultant vector)

Direction of forces are important, pay attention to +/-

Question 3

Vector Reduction

Answer 3

Subtracting forces

A single resultant vector can be “resolved” into separate component vectors

Force F can be broken into its two components: FH & FY

Question 4

Static rotary equilibrium

Answer 4

Internal torque = external torque

The net torque is equal to zero → the joint is not moving

Question 5

3 Types of Musculoskeletal Levers

Answer 5

First class (very few)
Second class (almost none)
Third class (most common)

Question 6

Why do muscles have small moment arms?

Answer 6

so they can move external forces over large distances quickly (force-distance tradeoff)

Question 7

Force-Distance Tradeoff

Answer 7

big force=large distance

small force =short distance

Question 8

Newton’s 1st Law

Answer 8

Law of Inertia - amount of force required to alter the velocity of a body

Question 9

Static equilibrium

Answer 9

linear or rotational velocity is 0

Question 10

Dynamic equilibrium

Answer 10

linear or rotational velocity is constant

Question 11

Mass of a body

Answer 11

describes its inherent resistance to a change in linear velocity

Question 12

Mass moment of inertia

Answer 12

describes the body’s inherent resistance to a change in angular velocity

indicated by I, expressed in units of kilograms per meter squared (kg∙m2)

Depends on the 1) amount of mass of a body and 2) distribution of mass of a body

Question 13

Newton’s 2nd Law

Answer 13

Law of Acceleration - force equals mass times acceleration

Refer to notes for Linear Force and Rotary Torque Acceleration relationships

Question 14

Newton’s 3rd Law

Answer 14

Law of Reaction - anytime a force is exerted on an object, the object exerts an equal but opposite force on the object

EX: Joint reaction forces, Ground reaction forces

Question 15

Joint reaction forces

Answer 15

force that is created in response to a muscle pulling one bone against the other during activation

The joint reaction force is always opposite the muscle force

Can compress or pull apart

Question 16

Ground reaction forces

Answer 16

“I hit the ground, the ground hits me back”

Question 17

Force has to be acting in what manner to contribute to torque?

Answer 17

1) acting at a distance
2) not parallel
3) not through the axis