PE - Biomechanical Principles and Levers

What are Newton’s 3 laws?

1. Law of inertia

2. Law of acceleration

3. Law of action / reaction

What is the law of inertia?

Every body continues in its state of rest or motion in a straight line, unless compelled to change that state by an external force acting upon it

How does mass change inertia?

The bigger the mass, the larger the inertia. Meaning more force will be needed to change its state of motion

What is the law of acceleration?

The rate of acceleration is proportional to the force causing it and the change that takes place in the direction which the force acts

How do you calculate acceleration?

Force = Mass x Acceleration

Due to objects not changing mass during sport what can be said?

“The greater the force applied, the greater the acceleration”

What is the law of action / reaction?

To every action there is an equal and opposite reaction

What is ground reaction force?

• The force exerted on the ground by the body

• An individual standing on the ground exerts a contact force (weight)

• At the same time, equal and opposite GRF is exerted by the ground on the individual

What is the point of concentration of mass?

The point of balance of a body

What are the 4 factors that affect stability?

1. The height of the centre of mass

2. Position of the line of gravity

3. Area of the base of support

4. Mass of the performer

How does the height of the centre of mass affect stability?

The lower the centre of mass, the more stable the performer

How does the position of the line of gravity affect stability?

The line of gravity should be central over the base of support to increase stability

How does the area of the base of support affect stability?

The more contact point there are to the floor, the larger the base of support, therefore increasing stability

How does the mass of the performer affect stability?

The greater the mass, the more stability because of an increased inertia

What is in the centre of a first class lever and which way does effort point?

• Centre = fulcrum

• Effort = downwards

What is in the centre of a second class lever and which way does effort point?

• Centre = resistance

• Effort = upwards

What is in the centre of a third class lever and which way does effort point?

• Centre = effort

• Effort = upwards

What is the effort / force arm of a lever?

The shortest perpendicular distance between fulcrum and effort

What is the resistance arm?

The shortest perpendicular distance between fulcrum and resistance

What are the advantages of a 2nd class lever?

• Effort arm = longer than resistance arm

• Generate much larger force

• Overcome heavy load

What are the disadvantages of a second class lever?

• Slow

• Limited range of movement

What are the advantages of a 1st / 3rd class lever?

• Resistance arm = longer than effort arm

• Large range of movement

• Resistance can be moved quickly

What are the disadvantages of a 1st / 3rd class lever?

• Can’t apply much force to move

• HArder to overcome a heavy load