06 Lever Mechanics

Question 1

The human skeleton has roughly how many bones?

Answer 1

206

Question 2

Together, the skeletal and muscular systems comprise the

Answer 2

Musculoskeletal system

Question 3

What determines the lever efficiency?

Answer 3

The position of insertion relative to joints determines the lever efficiency

Question 4

What is considered the most complex joint in the body and why?

Answer 4

The shoulder joint because it has the widest range of movement

Question 5

What type of joint exists at the shoulder and how is it formed?

Answer 5

Ball and socket - articulation of humerus with glenoid cavity of scapula

Question 6

Movement of the arm involves…

Answer 6

Muscles acting on the humerus at the shoulder joint Muscles that rotate the scapula

Question 7

Which muscles are involved in raising the arm (the upward rotators of the scapula)?

Answer 7

Upward rotators of the scapula - trapezius and serratus anterior

Question 8

Which muscles are involved in raising the arm (the abductors and flexors of the humerus at the shoulder joint)?

Answer 8

The deltoid, the supraspinatus and the pectoralis major

Question 9

Which downward rotators of the scapula are involved in lowering the arm?

Answer 9

The levator scapulae, the rhomboids and the pectorialis minor

Question 10

Which adductors and flexors of the humerus at the shoulder joint are involved in lowering the arm?

Answer 10

Latissimus dorsi and pectoralis major

Question 11

Protraction can occur at the shoulder, which muscles are involved in this?

Answer 11

Serratus anterior and pectoralis minor

Question 12

Retraction can occur at the shoulder, which muscles are involved in this?

Answer 12

Trapezius, rhomboids and latissimus dorsi

Question 13

What is a fulcrum?

Answer 13

The point against which a lever turns when it is supported

Question 14

What are the three possible arrangements of levers?

Answer 14

load, fulcrum effort fulcrum, load, effort fulcrum, effort, load

Question 15

What is the load in a biological lever?

Answer 15

The action

Question 16

What is the fulcrum in a biological lever?

Answer 16

The joint

Question 17

What is the effort in a biological lever?

Answer 17

The muscle

Question 18

There are three classes of lever, what are these?

Answer 18

Class 1, class 2 and class 3

Question 19

What is the method to remember the three types of lever?

Answer 19

fle

Question 20

Describe a class one lever?

Answer 20

The fulcrum is between the effort and the load

Question 21

Describe a class two lever?

Answer 21

The load is between the fulcrum and the effort

Question 22

Describe a class three lever?

Answer 22

The effort is between the fulcrum and the load

Question 23

Give three mechanical examples of a class one lever?

Answer 23

A seesaw, scissors (two class one levers) and a hammer

Question 24

Give two mechanical examples of a class two lever?

Answer 24

A wheelbarrow and nutcrackers (two class 2 levers)

Question 25

Give a mechanical example of a class three lever?

Answer 25

A castle drawbridge

Question 26

Give two examples of a biological class one lever

Answer 26

The extension of the elbow - pushing or pulling down Holding the head up

Question 27

Give an example of a biological class two lever

Answer 27

The plantarflexion of the ankle - for example pressing the brake in a car

Question 28

Give two biological examples of a class three lever

Answer 28

The flexion of the elbow (lifting) Elevation of the mandible

Question 29

Describe how the class 1 lever, the extension of the elbow works

Answer 29

Question 30

Explain how the class one lever of holding the head up works

Answer 30

Question 31

Explain how the class 2 lever, the plantarflexion of the ankle works

Answer 31

Question 32

Explain how the class three lever, flexion of the elbow works

Answer 32

Question 33

Explain how the class 3 lever, elevation of the mandible works

Answer 33

Question 34

In the class 3 lever of the elevation of the mandible, where is the fulcrum?

Answer 34

Temperomandibular joint

Question 35

In the class three lever of the elevation of the mandible, where is the effort?

Answer 35

The temporalis and massetter inserting on the muscle

Question 36

In the class three lever of the elevation of the mandible, where is the load?

Answer 36

The weight of the mandible

Question 37

Moment arms help to determine what in lever mechanics?

Answer 37

The strength of movement

Question 38

What does the efficiency of a lever depend on?

Answer 38

The moment arm of the load and the moment arm of the effort

Question 39

What is the equation for calculating efficiency of a lever mechanic?

Answer 39

Efficiency = moment arm of effort/ moment arm of load

Question 40

Which of the two would you expect to have a higher efficiency?

Answer 40

The first because the moment arm of effort is greater

Question 41

Why does a cat have a higher efficiency when comparing the moment arms

Answer 41

When using the equation, efficiency = ma effort/ ma load, the human comes out at a lower efficiency compared to the cat

Question 42

Efficiency is a trade of between which two factors?

Answer 42

Strength and speed

Question 43

Explain the difference between a and b

Answer 43

B the stride is longer, but the moment arm of load is increased so the efficiency is reduced

Question 44

Levers do two types of jobs, what are these?

Answer 44

They amplify force or they amplify distamce

Question 45

Give an example of a lever that amplifies force

Answer 45

A crowbar

Question 46

Give an example of a lever that amplifies distance

Answer 46

A cricket bat

Question 47

What is the critical features that distinguishes levers that amplify force and levers that amplify distance?

Answer 47

The relative distance of effort and load from the fulcrum

Question 48

Describe force amplifying levers

Answer 48

The distance to effort is greater than the distance to the load

Question 49

Describe levers that amplify distance

Answer 49

The distance to load is greater than the distance to the effort

Question 50

Most common tools are ____ amplifiers, (e.g. can opener, pliers, screwdrivers, spanners) but in nature _____ amplifiers are more common

Answer 50

Force, distance