As many contributory body pars as possible should be used
Body parts with the greatest inertia should lead the action ie the stronger, slower muscles
Body parts should be sequentially accelerated so that each preceding body part contributes optimally before the next body part comes into the action
Body parts should be sequentially stabilised so that each subsequent action may accelerate around a stable base.
A large throwing area
All activities should be performed with a partner, one throwing, and one marking. The throw should be carried out with maximum effort. Measure using stride length. The angle of release should be kept as consistent as possible.
Stay two metres away from the wall. Stand side on to the direction of the throw, with the feet shoulder width apart and the back knee straight. Rotate the trunk as far back as comfortable. Throw the ball using the hips, shoulders and arm, but make sure the body weight has been transferred before the arm begins to move.
Distance of throw:
During the throw, watch the action of the front leg.
In order that forces can be effectively applied, this
leg should stop or stabilise before the forward arm
Repeat Activity 5, but now step forward and throw the ball.
The back foot should be free to move or slide.
Distance of throw:
Because the forward swing of the arm does not occur until the centre of gravity has ceased its forward movement and stabilised over the front foot, the momentum of this forward movement cannot contribute to the total momentum of the throw.
In the throwing action how does the forward movement of the back foot assist force production?
Have the results shown a consistent increase in distance with each activity?
When considering both the vertical and horizontal component of accuracy, the performer must take into account:
The release height of the ball which controls the vertical component
The sideways alignment of the arm which controls the horizontal component.
Suitably marked wall
Stand 3 metres away from a wall.
Roll a ball along the floor to hit a target line at the bottom of the wall.
For this activity, the release height has stayed at the same level as it rolls across the floor to hit the target line. This has ensured that it has struck the wall at the same height each time. The vertical component has been controlled.
Stand beside a wall or blackboard. Extend an arm behind you and put the chalk against the blackboard. Keeping the arm straight, draw an arc on the board. Number the arc 1.
Repeat the activity, keeping the chalk in the same starting position. This time take a large step forward onto a straight leg and transfer the body weight onto the front leg before you draw the arc. Number the arc 2.
Repeat the second activity, but step forward onto a bent knee. Number the arc 3.
Repeat the third activity, but finish with a follow through, keeping the hand travelling in the desired direction of the force. Number the arc 4.
Draw and label the shape for each arc in the space provided.
Stand three metres from a corner in the gym with your throwing shoulder against the wall.
Perform an underarm throw releasing the ball at various heights. Make sure the arm is tight against the wall throughout the swing and to the point of release.
In this task the direction of the arm swing has been kept consistent, therefore no sideways movement of the arm during the swing, or the ball after release should be observed. The ball should have struck the wall at various heights along a perpendicular line almost coinciding with the corner line of the gym. Therefore the horizontal component of accuracy has been controlled.
Changes in rotational momentum can be affected by two things:
Increases or decreases in rotational speed
Changes to the distribution of mass around an axis point -= changes to rotational inertia.
L = Iw
Where L = rotational momentum
I = rotational inertia
w = rotational speed
A diver performing a forward tuck somersault cannot change the rotational momentum of the body after take off – there is nothing to push against in mid-air – rotational momentum can only be increased if you have something to push off Eg. A vaulting horse.
The rotational inertia can be changed mid-air = change in rotational speed
Some rotational momentum is lost due to air resistance – not much
For all intensive purposes it is conserved until a force is applied to change it – it will stay the same unless something is dome to change it (push off the vault = increase, hit the ground = 100% decrease).