Term
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Definition
A body continues in its state of motion unless acted upon by an external force.
- The size of the force required to change the state of motion of an object depends on the mass of the object. The greater the mass of the object, the greater the force required to move it. |
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Term
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Definition
The term used to describe the amount of resistance to a change in an objects state of motion
- is directly proportional to an objects mass |
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Term
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Definition
"The rate of change of acceleration to a body is proportional to the force applied to it and inversely proportional to the mass of the object"
Force = mass x acceleration (m/s/s) |
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Term
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Definition
"The tendency for something to keep moving"
Momentum = mass x velocity
- an object can only have momentum if its moving
- the greater its momentum, the more force required to either stop or slow down the object
- as a result, when two bodies collide the one with the most momentum will be less affected |
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Term
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Definition
"When two objects exert a force upon each other, the forces are opposite in direction and equal in magnitude"
- this law applies directly to the concept of conversion of momentum
- it explains that when collisions occur, an equal and opposite force occurs resulting in a transfer of momentum from one object to another
Eg. when swinging a baseball bat towards a ball, both the ball and the bat possess a certain amount of momentum before collision. Upon collision, the ball explodes away while the baseball bat rapidly decelerates during the follow through |
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Term
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Definition
"The change in momentum of an object"
Impulse = force x time
- The loner the force can be applied to the object and the greater the size of the force applied will increase the objects impulse
EG. Tennis racquets
- looser strings results in the ball on the racquet for longer and therefore more power and less control
- tighter strings result in the ball on the racquet for less time and therefore more control and less power |
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Term
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Definition
Ideally looking to maximise both force and time, however the human body rarely allows for this to happen.
Eg. in hockey, a hit will place a large force but over a small time but a drag flick would use a smaller force over a longer period of time, both result in an increase in momentum |
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Term
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Definition
To stop a force, usually you would increase the time component so we can reduce the peak force.
Eg. A cricket ball is hit towards a fielder. The fielder wishes to stop the ball |
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Term
| Co-efficient of Restitutuion |
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Definition
"The elasticity of the collision between an object and a given surface, measuring how much energy remains in the object after a collision takes place."
A COR of 1represents a perfectly elastic collision (the rebound distance is equal to the height dropped)
A COR of 0 represents a perfectly inelastic collision, effectively stopping at the surface with which it collides (no bounce) |
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Term
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Definition
| "the measure of how much rebound exists following a collision" |
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Term
| Factors affecting the COR |
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Definition
1. Temperature
A higher temperature will results in an increase in the COR
Eg. In squash the ball will have a higher COR if it is warmed up and will increase the 'bounciness'
2. Equipement and materials
Condition of the balls - a new ball will be in perfect condition (perfectly elastic)
Type of equipment - Baseball, wooden bats compulsory, aluminium have a higher COR
Type and condition of the playing surface
Eg. Tennis, Clay court (high COR) vs grass court (low COR)
3. Velocity of the colliding bodies
The greater the velocity, the greater the compression of the object and the slower its return to normal shape - th eincreased velocity reduces the COR |
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Term
| Factors that create angular motion |
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Definition
Caused by the application of an eccentric (off-centre) force
If only one eccentric force is applied to the object, both linear and angular motion occur.
If one end of the object is fixed, then only angular rotation occurs
To increase an object angular rotation
- increased amount of force applied
- increase the distance from the axis by which the force is apllied |
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Term
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Definition
"A turning force which is a force being applied around a pivot"
The magnitude of the turning point is called the moment of force or torque.
Torque = force x distance |
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Term
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Definition
"Refers to the resistance of a rotating object to change its state of motion"
Moment of Inertia = objects mass x radius of rotation |
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Term
| Conversion of angular momentum |
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Definition
"A spinning body will continue spinning indefinitely unless acted upon by an external force"
Increasing angular momentum
- increase linear momentum
- improve segmental interaction at take off |
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Term
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Definition
"A rigid bar resting on a pivot, used to move a heavy or firmly fixed load with one end when pressure is applied to the other."
Components:
1. weight/resistance
2. axis/pivot
3. application of force
Functions:
- increase application of force by making the force arm longer that the resistance arm
- increase speed of movement by making the force arm shorter that the resistance arm |
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Term
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Definition
F_A_R - axis in the middle
Eg. (See-saw) The effort comes from the person pushing down whilst the resistance come from the person on the other end.
Body: neck and shoulders and head |
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Term
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Definition
A_R_F - resistance in the middle
An example of the 2nd class lever is a wheelbarrow, where a large force arm ensures increased strength to an object can be applied
Eg. Push up |
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Term
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Definition
A_F_R - force in the middle
Most common type of lever in the human body as we are mechanically built for speed.
A large resistance arm ensures maximum speed can be obtained
Bicep Curl, used with striking instruments eg. Golf club
By increasing the length of the resistance arm, it is possible to generate greater velocity of the striking surface, resulting in greater force being transferred onto the ball.
An increase in the length of the lever may result in an increased weight, affecting control
Gripping the bat in cricket at the very edge of the handle is used to create a longer resistance arm and therefore bat velocity |
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Term
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Definition
1. A smaller force can balance a larger resistance when the force arm is longer than the resistance arm
2. A force can move resistance through a greater range of motion when the force arm is shorter that the resistance arm |
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Term
| Factors affecting the use of levers |
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Definition
1. Length of the lever
- velocity is greatest at the distal end of a lever
- longer the lever, the greater the velocity at impact
- increase club length increases velocity and momentum at impact provided the athlete can control the lever - longer usually means heavier
2. The inertia of the lever
- the longer the lever, the heavier it usually is and therefore the more difficult to rotate
- by choking down the club in striking sports, athletes can reduce the rotational inertia of the implement therefore making it easier to swing
3. Amount of force
- the amount of force the athlete is able to generate via their muscles determines the length of the lever the athlete should use
- ist crucial that athletes do not use longer levers if they cannot control them or they are not physically strong enough |
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Term
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Definition
| "The natural science of fluids (liquids and gases) in motion" |
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Term
| Factors affecting Fluid resistance |
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Definition
1. Viscosity
- "a measure of the fluids resistance to flow"
- eg. honey is more viscous than water, but water is more viscous than air. Therefore a swimmer would obviously experience more viscosity than a runner
2. Density
- "Mass per unit per volume"
- generally the more dense the fluid, the greater the fluid.
- fluid is affected by: humidity, temperature and pressure |
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Term
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Definition
"A type of fluid flow in which fluid moves smoothly in individual layers or streams over the object"
- this type of flow moves the point of separation towards the front of the object, thus increasing drag |
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Term
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Definition
"Fluid in which the velocity at any point of impact varies erratically"
- the type of fluid flow in which the boundary layer becomes so turbulent that the point of separation moves further back on the object, thus reducing drag |
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Term
| Boundary layer separation |
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Definition
"Where the boundary layer breaks away from the ball"
- the earlier the boundary layer separation, the greater the pressure gradient between the front and back of the ball
- leads to increase drag
- laminar flow (large turbulent pocket at the back of the ball)
- turbulent flow (small turbulent pocket at the back of the ball) |
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Term
| Factors affecting boundary layer separation |
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Definition
1. Velocity
- low velocity = boundary layer clings to surface, minor drag
- high velocity = separation occurs further forward, increased drag
2. Surface roughness
- rough surfaces reate turbulent boundary layer, reducing the effect of drag. Eg. Golf ball (dimpled vs smooth) |
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Term
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Definition
1. Drag co-efficient
- measure used to quantify the drag or reisstance of an object in a fluid environment
2. Cross sectional area (CSA)
- linear relationship exists between CSA exposed to aire and drag
- increased CSA = increased drag
3. Speed
- the faster the ball moves through the air, the earlier the boundary layer separates form the ball creating a large pressure differential between the front and rear of the ball
4. Surface roughness
- rougher surfaces allow for the air stream to cling to the ball for longer periods, resulting in a smaller pressure differential between front and back of the ball and hence less drag
5. Mass
- greater the mass of the ball, the lesser the effect of drag
6. Shape
- oval vs round ball
- oval (gridiron) ball cuts through the air more cleanly than a round (soccer) ball
- gridiron encourages the air stream to cling to the contours of the ball all the way to the end of the tail
- results in a smaller pressure differential between the front and back of the ball and therefore less drag |
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Term
| Environmental factors affecting drag |
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Definition
1. Air density
a) higher altitude results in reduced drag
b) smaller the object, greater the effect
c) easier to hit a home run in higher altitude
2. Atmospheric pressure
- increase pressure = increased density = increased drag
3. Humidity
- increased humidity = increased density = increased drag
4. Temperature
- increased temp = decreased density = decreased drag |
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Term
| Sporting application of drag reduction |
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Definition
1. Swimming - swim suit design have developed to improve buoyancy and reduce drag
2. Cycling - aerodynamic helmets, bike design (disc wheels) and tight fitting clothing have all helped to reduce drag
3. Ski jumping - ski and helmet design and tight fitting clothing have all been improved to reduce drag |
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Term
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Definition
"Friction produced between fluid and surface of a moving object"
- skin friction or viscous drag |
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Term
| Factors affecting surface drag |
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Definition
1. Relative velocity of moving object
2. Relative roughness of surface object
- athletes wear tight fitting clothing in speed skating, cycling etc, reducing the surface drag
3. Viscosity of the fluid
4. Surface area of the object
- in rowing and cycling, equipment has been designed to try to reduce the size of the surface area in contact with the surface |
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Term
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Definition
"Resistance created by pressure differential between front and back of an object moving through a fluid"
- profile drag |
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Term
| Factors affecting form drag |
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Definition
1. Cross sectional area of object presented to the fluid
- cyclist in upright vs crouched position
2. Velocity of the object
- at higher speeds, athletes can experience greater levels of form drag
3. Surface roughness
- rougher surfaces cause the air to cling to the surface for longer periods, causing a later separation point and hense less drag
4. Shape of the object
- round vs oval ball |
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Term
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Definition
"Resistance formed by a creation of waves at the point where air and water interact"
- seen as the major type of drag on a swimmer |
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Term
| Factors affecting wave drag |
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Definition
1. Relative velocity of the wave
- greater the velocity, greater the wave drag
2. Technique
- by using a more streamlined technique, swimmers can reduce the effect of wave drag
- swimming underwater further reduces wave drag
- over reaching in backstroke will cause the body to move through its own waves causing resistance
3. Open water (ocean) vs closed conditions (pool)
- lane ropes used to reduce wave drag by helping to dissipate moving surface water |
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Term
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Definition
"The component of force that acts perpendicular to the direction of flow
- will act at a right angle to the direction of motion, meaning it can act both upwards and downwards
- only occurs in objects which are spinning or not perfectly symmetrical
- lift is created by the different pressures on opposite sides of an object due to fluid flow past the object
Eg. aeroplane wing (hydrofoil) creates lift in a upwards direction to keep it in the air
Eg. racing car creates downwards direction to keep it on the ground |
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Term
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Definition
"Velocity is inversely proportional to pressure"
- high velocity = low pressure
- low velocity = high pressure |
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Term
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Definition
"The effect of rotation on an object's path as it moves though fluid"
- it applies Bernoulli's principle to explain the effect spin has on the trajectory or flight path of an object |
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Term
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Definition
Golf - application ob back spin allows players to attack the green, ensuring the ball approaches the flag from a steeper angle
Tennis - application of back spin can be used as a defensive option, allowing the player to regain court position or as an attacking position, through the use of the drop shot
Soccer - application of back spin used by players to kick the ball greater distances by increasing the amount of time the ball is in flight |
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Term
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Definition
| Tennis - application of top spin allows the players to hit the ball with greater force whilst reducing risk as the ball will dip during it's flight (Rafael Nadal) |
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Term
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Definition
Golf - application of side spin (draw, fade) allows players to work the ball around corners, reducing reducing risk in game play
Soccer - application of side spin by players such as David Beckham can be used to great effect when shooting on goal and passing to team mates |
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Term
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Definition
1. Preparation
- ensure you have a large base to ensure you transfer momentum from one segment to the next around a stable base
- this is achieved by: taking large strides towards the target and having a large base of support |
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Term
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Definition
2. Execution
- through the application of back spin to the ball (golf drive and soccer kick for maximum distance) this creates a Magnus lift force which optimises the vertical and horizontal displacement of the ball when other factors remain constant |
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Term
| Segmental interaction/ Coordination continuum |
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Definition
1. Preparation
- each subsequent segment should begin to move as the proceeding segment reaches its maximum velocity to ensure optimum momentum is transfered to the ball (same for golf, baseball pitching and soccer kicks for maximum distance)
- in order to maximise the number of segments, adopt a side on position to the target to ensure, legs, hips, shoulders etc are used in the execution of the skill
- ensure big body parts of the legs and hips move first and smaller parts of the wrist move last to ensure optimal momentum is passed onto the ball at the point of release
- in baseball pitching, the application of an eccentric force on the ball can create side spin from either left to right or right to left which can produce optimal performance for the pitcher in terms of pitch variability
3. Follow through phase
- as all three skills (baseball, soccer and golf) require force to be developed sequentially for maximum force, it requires the athletes to
> follow through towards the target to ensure safe dissipation of force and ensure no deceleration of final segment at point of release/impact
> ensure all forces are directed towards the target (more accuracy than force production) |
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Term
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Definition
1. Preparation phase
- by adopting a side on position and extending the throwing arm/leg/club back during the preparation phase allows for maximal for time to be applied
- by effective segmental interaction, it allows for maximum force to be developed over the movements |
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Term
| Inertia (Moment of inertia) |
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Definition
1. Preparation
- at the commencement of the movement, reduce the balls/legs/drivers moment of inertia by bending elbow/knee, bringing the mass closer to the axis of rotation, reducing the moment arm and reducing the moment of inertia
- as velocity increases throughout the preparatory swing, the ball/leg/driver is moved further away from the axis of rotation to increase the moment of inertia. This is done in attempt to maximise both the angular velocity and the moment of inertia
2. Execution
- as velocity increases through the preparatory swing, the ball/leg/driver is moved further away from the axis of rotation to increase the moment of inertia. This is done in an attempt to maximise both angular velocity and the moment of inertia of the lever at the point of contact |
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Term
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Definition
1. Preparation phase
- by having a greater range of motion at the shoulder/hip joint, it ensures that the lever is taken as far back as possible during the preparatory backswing, so that velocity fo the lever can be developed over the largest distance possible
2. Execution phase
- angular velocity is greater at the distal end of the lever, therefore by maximising the length of the lever at the point of release ensures the ball/leg/driver travels with maximum velocity to the point of execution (release of ball/contact on ball) |
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Term
| Force motion (Newton's laws) |
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Definition
2. Execution phase
- throughout the application of Newton's 3 laws, athletes can change the state of motion of an object
I. Newtons first law (inertia)
- " a body continues in its state of motion or state of rest unless acted upon by an external force"
- the golf ball will remain stationary unless acted upon by an external force (muscles)
II. Newton's second law (acceleration/momentum)
- "the rate of change of acceleration of a body is proportional to the force applied to it, and inversely proportional to the mass of the object"
- as the mass of the golf ball are relatively constant in their own context, the rate of change of acceleration of the ball is directly proportional to the force applied
- if the same force was applied to a soccer ball (weight varies in wet conditions), the rate of change of acceleration would see that the ball with the lesser mass (golf ball) would accelerate faster whilst a ball with a greater mass (soccer ball) would accelerate the slowest
III. Newtons third law (action/reaction)
- "for every action there is an equal and opposite reaction. Opposite in terms of direction and equal interms of magnitude"
- by applying a greater ground reaction force, and equal and opposite reaction force will be transfered from the ground, through the body and to the ball |
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Term
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Definition
2. Execution phase
- to maximise distance, with all other factors help equal, the ball will be kicked/struck at approximately 45 degrees
- in baseball, the pitcher delivers his pitch a significantly less than 45 degrees as maximal distance is not a consideration and the velocity of he pitch is the main consideration |
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