Flashcards in Biomechanics Pt. 3 (9/5d) Deck (17)

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1

## For every force, there is an ___ and ___ force

### equal and opposite

2

## Vector Composition

###
Adding forces

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

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

3

## Vector Reduction

###
Subtracting forces

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

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

4

## Static rotary equilibrium

###
Internal torque = external torque

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

5

## 3 Types of Musculoskeletal Levers

###
First class (very few)

Second class (almost none)

Third class (most common)

6

## Why do muscles have small moment arms?

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

7

## Force-Distance Tradeoff

###
big force=large distance

small force =short distance

8

## Newton's 1st Law

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

9

## Static equilibrium

### linear or rotational velocity is 0

10

## Dynamic equilibrium

### linear or rotational velocity is constant

11

## Mass of a body

### describes its inherent resistance to a change in linear velocity

12

## Mass moment of inertia

###
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

13

## Newton's 2nd Law

###
Law of Acceleration - force equals mass times acceleration

Refer to notes for Linear Force and Rotary Torque Acceleration relationships

14

## Newton's 3rd Law

###
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

15

## Joint reaction forces

###
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

16

## Ground reaction forces

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

17