Biomechanics

Linear Motion

Where movement is along a straight or curved line, there is no rotation & all body parts move in the same direction at the same speed. e.g. a cyclist who stops pedalling

Rectilinear Motion

Movement is linear & occurs through a straight line e.g. a basketball chest pass

Curvilinear Motion

Movement is linear by objects move through a curved trajectory. e.g. the trajectory of the ball as it is shot into the goal in netball

Angular Motion

Where all the parts of a body move through a rotational pathway, through the same angle, in the same direction & at the same time. It is the rotary movement without an axis. e.g. when a gymnast performs a giant on the bar

General Motion

A combination of linear & angular motion. e.g. a cyclist moving in a straight line as a result of the rotation of the legs about the hip joint

Distance

How far you have travelled from your start to finish point, regardless of direction. Measured in total distance covered

Displacement

Measures the overall change in position of a person and is measured in magnitude & direction

Speed

A measure of the distance an object travels per unit of time.

Distance travelled / by time taken

Velocity

Speed in a given direction

Displacement / time

Acceleration

The rate at which the velocity of a body changes with respect to time

Change in velocity / time

Acceleration due to Gravity

The naturally occurring force resulting in downward acceleration on a body at a constant rate of -9.8m/s

Uniform acceleration

When a body accelerates at a constant rate in both magnitude & direction

Angular displacement

The difference in the angle between the start & end position of the body

Angular distance

The sum of all the angles as a body moves from its start position to its end position

Force

An interaction that, when unopposed, will change the. motion of an object

Mass x Acceleration

External Forces

The result of the interaction between the body & the environment e.g. gravity

Internal Forces

Result from structures of the body that interacts to produce movement e.g. the action of muscles & tendons that act together to produce forces causing movement

Contact Forces

A type of external force that acts on an object that comes into direct contact with another e.g. frictional or air resistance forces

Non-contact Forces

A type of external force that acts on objects without coming into direct contact with one another e.g. gravity

Newton’s 1st law

A body continues in its state of rest or state of motion unless acted upon by force

Inertia

The amount of resistance to a change in a object’s state of motion

Newton’s 2nd law

The acceleration of a body is proportional to the force applied to it & inversely proportional to the object’s mass

Momentum

A measure of the amount of motion possessed by a moving body.

Mass x Velocity

Impulse

The application of force over a period of time to change the momentum of an object

Force x Time

Newton’s 3rd law

For every action, there is an equal & opposite reaction

Ground reaction forces

The force exerted by the ground on a body in contact with it

Conservation of momentum

The total momentum of two objects before & after impact are equal

Resistance

The weight or load to be moved

Axis

The pivot point or fulcrum around which the lever rotates

Effort

The application of force or effort

Effort/force arm

The distance between the fulcrum & the point at which the force is applied

Resistance arm

The distance between the fulcrum & the centre of the resistance

Effort force

Force exerted on the lever

Resistance force

Force exerted by the lever

Force multiplier

Increasing the application of force by making the force arm longer than the resistance arm

Speed multiplier

Increasing movement speed by making the resistance arm longer than the force arm

1st class lever

The axis is located in the middle, with the force & resistance on either side e.g. heading a soccer ball

2nd class lever

The axis is located at the end, with the resistance in the middle & force applied at the end. e.g. performing a calf raise

3rd class lever

The axis is located on one end, with the application of force in the middle & resistance applied at the opposite end. e.g. a bicep curl

Projectile

An object propelled into the air or water & affected only by the forces of gravity & air resistance

Static balance

The ability to hold a stationary position. e.g. holding a handstand

Dynamic balance

The ability to hold a moving position to execute an outcome. e.g. riding a skateboard

Centre of Gravity

The theoretical point in an object, located either inside or outside of the body, where all of the body’s mass is equally distributed

Line of gravity

An imaginary vertical line passing downwards through the centre of gravity to the ground or surface the person is on

Base of Support

The area bound by the outermost regions of contact between a body & support surface