Lever Mechanics Lecture 6

Question 1

The musculoskeletal system

Answer 1

The skeleton and skeletal muscle act together

Question 2

Shoulder movement

Answer 2

Ball and socket joined, formed by articulation of humerus with glenoid cavity of scapula
Movements of the arm involves muscles acting on the humerus at the shoulder joint and muscles that rotate the scapula

Question 3

Shoulder movement – raising the arm

Answer 3

Upwards rotators of the scapula

Abductors and flexors of humerus at shoulder joint

Question 4

Shoulder movement- lowering the arm

Answer 4

Downwards rotators of the scapula

Adductors and flexors of humerus at shoulder joint

Question 5

Lever mechanics- three labels

Answer 5

Load (=action)
Fulcrum (=joint)
Effort (=muscle)

Question 6

Class 1 lever

Answer 6

Fulcrum between effort and load 
Effort and load both act downwards 
Seesaw
Scissors (2 class 1 levers) 
Hammer

Question 7

Class 2 levers

Answer 7

Load between fulcrum and effort
Wheelbarrow
Nutcrackers (2 class 2 levers)

Question 8

Class 3 levers

Answer 8

Effort between fulcrum and load

Castle drawbridge

Question 9

How to remember classes of levers

Answer 9

FLE (elf backwards)

Question 10

Examples of class 1 levers

Answer 10

Extension of elbow (pushing or pulling down)

Holding the head up

Question 11

Examples of class 2 levers

Answer 11

Plantarflexion of ankle (e.g. pressing brake in car)

Question 12

Examples of class 3 levers

Answer 12

Flexion of elbow (lifting)

Elevation of mandible

Question 13

Moment arms

Answer 13

Help to determine strength of movement
Moment arm of load= length from fulcrum to end of load
Moment Aron of effort= length from fulcrum to effort

Question 14

Efficiency equation

Answer 14

Moment arm of effort / moment arm of load

Question 15

What is efficiency a trade off between

Answer 15

Strength and speed

Question 16

Levers that amplify force

Answer 16

E.g. a crowbar
Effort force < loading force
Distance to effort> distance to load

Question 17

Levers that amplify distance

Answer 17

E.g. a cricket bat
Effort moves shorter distance than load
Distance to load > distance to effort