Chapter 5.1 (Biomechanical Principles and Levers)

Question 1

Define linear motion

Answer 1

Motion in a straight or curved line, with all body parts moving the same distance, at the same speed, in the same direction

Question 2

Define Newton’s first law of motion (law of inertia)

Answer 2

The resistance an object has to experience for a change in its state of motion

• If an object is at rest, it will remain still
• If an object has a velocity it will continue at that velocity until another force is exerted on it

Question 3

Define Newton’s second law of motion (law of acceleration)

Answer 3

The magnitude and direction of the force determines the magnitude and direction of the acceleration

Question 4

Define Newton’s third law of motion (law of action/reaction)

Answer 4

For every action, there is an equal and opposite reaction

Question 5

Define ground reaction force

Answer 5

The equal and opposite force exerted on a performer who applies a muscular force on the ground

Question 6

Define scalar quantity

Answer 6

When measurements are described in terms of just their size or magnitude

Question 7

Define speed

Answer 7

The rate of change of position

Question 8

Define centre of mass

Answer 8

This is the point of balance

Question 9

What are the factors affecting stability?

Answer 9

• The height of the centre of mass - lower centre of mass = better stability
• Position of the line of gravity - should be over the base of support
• Area of the support base - the more contact points, the larger the base of support
• Mass of the performer - often the greater the mass, the more stability

Question 10

Define fulcrum

Answer 10

The point about which the lever rotates

Question 11

Define resistance

Answer 11

The weight to be moved by the lever system

Question 12

Define effort

Answer 12

The force applied by the user (muscle) of the lever system

Question 13

What is the first class lever? Give an example

Answer 13

• The fulcrum lies between the effort and resistance

- Movement of the head and neck during flexion and extension and tension of the elbow

Question 14

What is the second class lever? Give an example

Answer 14

• The resistance is between the fulcrum and and effort

- Plantarflexion of the ankle

Question 15

What is the third class lever? Give an example

Answer 15

• The effort is between the fulcrum and the resistance

- Hip, knee and elbow flexion

Question 16

Define force arm

Answer 16

The length of the line between where the fulcrum and effort are labelled

Question 17

Define resistance arm

Answer 17

The length of the line between where the fulcrum and the resistance are labelled

Question 18

Define mechanical advantage

Answer 18

Where the force arm is longer than the resistance arm

Question 19

Define mechanical disadvantage

Answer 19

Where the resistance arm is longer than the force arm