What is the relationship between the centre of mass and the application of force ?

A force who’s line of application passes through the centre of mass causes the resulting motion to be linear

A force who’s line of application passes outside its centre of mass causes the resulting motion to be angular. Called an eccentric force = rotation = angular motion

Define a scalar and vector quantity

Scalar - a scalar quantity has only magnitude e.g. speed, mass, distance

Vector - a vector quantity has both magnitude and direction e.g. displacement, velocity, acceleration, momentum, weight

Give the formula for weight

Weight (N) = mass x gravitational force

Weight is a vector quantity

Define both displacement and distance

Distance - Measured in metres. The path a body takes as it moves from the starting to finishing position. Scalar quantity.

Displacement- Measured in metres. Shortest route in a straight line between start and finish position. Vector quantity.

Define speed

Speed - the rate of change of a position. Is a scalar quantity

Given by the formula - distance / time

Define velocity

Velocity - Velocity refers to how fast a body travels in a certain direction. It is the ‘rate of change of displacement. It is a vector quantity.

Velocity = displacement (M) / time (s)

Define acceleration

Acceleration - the rate of change of velocity. When velocity increases, positive acceleration occurs whilst when velocity decreases negative acceleration occurs.

Acceleration - change in velocity / time

Define momentum ?

Is the product of mass and velocity of an object. It is a vector quantity.

Momentum (kg/ms) - mass(kg) x velocity (m/s)

What is the conservation of momentum ?

This occurs when an object or a performer is in flight

When in flight neither mass nor velocity can be altered

What are the 2 type of forces and their definitions ?

Internal forces - generated by the skeletal muscle

External forces - comes from outside the body

Give examples of internal forces

In a layup the forces are generated by the gastrocnemius, quadriceps and gluteals that contract concentrically to plantarflex the ankle & extend the knee and hip in a jump

Give examples of external forces

Air resistance, gravity, weight

How can you categorise external forces ?

Horizontal forces - friction and air resistance

Vertical forces - gravity and weight

What Is a reaction force ?

A force which is generated when 2 objects are in contact with each other

Newtons 3rd law - for every action there is an equal and opposite reaction

What 2 types of friction forces are there ?

Static - force exerted when there is no motion between 2 objects. Force that keeps an object at rest

Sliding - When 2 bodies in contact have the tendency too slip / slide over one another. Friction acts in opposition to motion

What 3 factors affect friction ?

1) The roughness of the surface

2) The mass of the object

3) Temperature of the 2 surfaces. Increase in temperature reduces the friction

What 3 factors effect air resistance ?

The velocity of the moving object

The frontal cross sectional area of the moving body

The shape and surface characteristics of the moving body