© Tony Fagelman 2006
Take-Off
• Time is a major factor• Take-off is the most
important part of any skill
• Without a good take-off, the skill cannot be performed correctly
© Tony Fagelman 2006
Flight
• This is 2nd part of any movement using the trampoline
• The flight requires control and phasing
© Tony Fagelman 2006
Landing
• Safety is a major factor
• Performer must be in control
• Preparation for next skill
© Tony Fagelman 2006
Newton’s Laws of Motion
• 1st Law :– A body will continue in its uniform state of motion or
rest unless acted on by an external force.• 2nd Law:
– The rate of change of momentum is proportional to the force causing it and the change takes place in the direction in which the force acts.force = mass x acceleration
– if mass is constant, acceleration is proportional to the applied force
• 3rd Law:– For every action there is an equal and opposite
reaction
© Tony Fagelman 2006
Centre of Mass
• The point though which the line of force of “attraction to the earth” takes place.
Centre of Mass
© Tony Fagelman 2006
Forces
• Push & Pull– A force is needed to:
• Start a motion• Change the rate of motion• Change the direction of motion• Cause motion to stop
© Tony Fagelman 2006
TORQUE
• The Rotational push or pull• Caused by a FORCE
• Eccentric or Off-Centre Force also called Torque– This will always create rotation– A torque whose line of action does not
pass through the centre of mass of the body on which it acts
© Tony Fagelman 2006
Displacement of COM
• What happens when we displace the Centre of Mass outside the body?
Centre
of
Mass
© Tony Fagelman 2006
Linear Movement
• Movement in a straight line• Remember Newtons’ 1st
law– A body will carry on unless
acted on • A trampolinist will bounce
upwards until gravity pulls them back down again
© Tony Fagelman 2006
Angular Movement
• An off-centre force acting around the Centre of Mass will create angular movement (Somersault rotation) (Remember displacement of COM)
• Rotation around an axis• Somersaulting demonstrates
both Linear Movement and Angular Movement
© Tony Fagelman 2006
Axis of rotation
• somersault axis• twisting axis• side somersault axis
Any rotation can be described using the 3 axis.
© Tony Fagelman 2006
Inertia
• The resistance of a body to change • Inertia is measured by Mass
• Or Not… as the case may be
© Tony Fagelman 2006
Momentum
• Is the amount of Linear Movement “energy” in a body as it moves
• It is the “quantity” of motion– Velocity x Mass
© Tony Fagelman 2006
Conservation of Linear Momentum
• Conservation & Creation– Whatever you put into a closed system is
what you have.• Remember Newton’s 1st Law• Can a performer do anything to help themselves to
safety if they do not have sufficient somersault rotation?
© Tony Fagelman 2006
Changing Linear Momentum
• All changes in Linear momentum are caused by external forces.
• The changes are determined by the size and direction of the force
© Tony Fagelman 2006
Projectile Motion
• when a performer is in flight he/she is a projectile
• the only force acting on them is the force of gravity
• the flight path is predetermined and will not change once in flight.
• the CoM will follow a parabolic flight path
© Tony Fagelman 2006
Moment of Inertia
• The measure of the body’s reluctance to start rotating (or change direction) around an axis
© Tony Fagelman 2006
Angular Speed
• The rate of rotation around an axis
• To control angular speed in flight (by changing the moment of inertia), the body can change shape
© Tony Fagelman 2006
Angular Momentum
• The amount of rotational energy in a body as it rotates around an axis
© Tony Fagelman 2006
Changing Angular Momentum
• These are caused by external torques.
• The changes are determined by the size and direction of the torque
© Tony Fagelman 2006
Conservation of Angular Momentum
• Angular momentum will remain the same until changed by an external torque– Tucking when
somersaulting– Straightening when
somersaulting
© Tony Fagelman 2006
Mechanics of somersaulting
• Creation of a somersault
• Angular movement is caused by TORQUE
• Torque = Force x Perpendicular distance from axis of rotation
© Tony Fagelman 2006
Early Twist
• Twist is initiated from the bed
Arms are set whilst in contact with the bed. Movement is initiated
Trampolinist has left the bed
Arms are brought together to allow twist to continue
© Tony Fagelman 2006
Late Twist
• The Twist is initiated in the air– There are a number of
theories given to this action.
© Tony Fagelman 2006
Tilt Twist
• By moving the body outside the line, twist can be initiated
• The greater the tilt, the greater the twist