Biomechanics Flashcards
define the conservation of momentum and state the formula
A moving object has momentum unless a force is applied to the object to increase or decrease the momentum. momentum is conserved
Formula: mass x velocity
define the impulse momentum relationship
and provide an example
When a force is applied to a ball momentum changes impulse is expressed by four times time newton second law is often referred to as the impulse momentum relationship
example: a hockey player who drags out a penalty shot and hold the stick on the part for the longest amount of time will allow for more force
define coefficient restitution
and what Is the formula
COR measures the elasticity of the collision between an object and a given surface. It measures how much energy remains in the object after a collision takes place.
formula: height of rebound/ height of drop
define moment of inertia
list the formula
inertia: amount of resistance to a change in an objects state of motion
moment of inertia: the resistance to rotational motion the grater the moment of inertia the greater amount of torque required to impart the same amount of angular acceleration in the body.
formula: I = mr^2
define angular momentum
the quantity of angular motion possess by a body angular momentum = angular velocity x moment of inertia
what is a leaver
objects which turn about a fixed point (fulcrum or axis)
outline the difference between the 3 leavers
First class lever the fulcrum is located in between the resistance and force application the function is to increase speed which a load or object can move
second the fulcrum is located at the end of the lease or rather resistant is between the fulcrum and the force
Third class lever the fulcrum is at the end of the lever
Outline the difference between a force arm and a resistance arm
how can this effect the movement of the lever and the mechanical advantage of the lever
Foursome or effort arm is the distance from the point where the force is applied to the fulcrum for example the bicep attaches to the elbow the longer the foursome the less effort required to move the resistance
The resistance arm also known as the load arm is the distance from the load to the fulcrum the longer a resistance arm the quicker the system can move
mechanical advantage can be measured force arm/ resistance arm
when the force arm is longer than the resistance arm the mechanical advantage is better this means the system is more effective at moving heavy loads
conversely when the resistance arm is longer than the effort arm the mechanical disadvantage occurs though the lever can mover quickly it is not as capable of moving heavy loads
how can you increase the mechanical advantage of a lever
- bigger leaver
- shorter force arm
- longer resistance arm
what factors effect the use of a lever
Length of the lever
The inertia of the lever
The longer the lever, the heavier it usually is and therefore the more difficult it is to rotate
The amount of force
The amount of force an athlete is able to generate via their muscles determines the length of the lever the athlete should use
define balance force motion force time inertia optimal projection range of motion and spend
BALANCE
The ability to neutralise forces that disturb equilibrium.
Ensure you have a large stable base to ensure all segments rotate around a stable base.
FORCE – MOTION (Newton’s Laws)
refers to the application of force to create motion.
Therefore using Newton’s Laws, apply each/any of these to striking for maximum velocity
FORCE – TIME (IMPULSE)
Impulse is the application of force over a period of time to change the momentum of an object. the greater time applied the bigger impulse. impulse = force x time
INERTIA
Is the term used to describe the amount of resistance to a change in an objects state of motion a body will remain at least unless acted on by an external force (the heavier the object is the more effort required to make a movement
OPTIMAL PROJECTION
When angle, velocity and height of release combine to meet the demands of the task If the demands of the task are to maximise distance, therefore the athletes must; Maximise velocity Maximise height of release and Angle of release
RANGE OF MOTION (ROM)
Refers to the extent of motion around a joint.
A larger ROM at the shoulder joint ensures velocity of the bat and the ball can be developed over a larger distance resulting in a greater transfer of momentum onto the ball.
SPIN
Term used to describe the effect of rotation on an object’s path as it moves through a fluid. lift comes into play if more spin is imparted on an object.
eg. Through the application of back spin to the ball, it optimises the ball’s time in flight (as a result of the Magnus Effect) and therefore maximises the distance achieved.
list 2 examples of each type of leaver
1st. in the body
2nd. not in the body
first class: in the body a athlete who throws a javelin: there elbow joint is the fulcrum the force is provided by the hand and resistance by the upper arm
out side the body: a see saw
second class: standing on your tip toes the fulcrum is the ball of the foot the lead is the ankle and the force is the gastronemius out side the body is a wheel barrow
third class: in the body a bicep curl the elbow is the fulcrum the weight is the resistance and the bicep insertion point is the force out side the body is a shovel
define touque and list the formula
the measurement of turning effect created in result of a eccentric force being applied around a pivot or an axis
Torque = Force x perpendicular Distance of leaver arm
explain the coordination continuum
Involves sequencing and timing the bodies action to create a movement the optimal timing depends on what activity you are doing when activities require high force simultaneous sacramental movement is most affected were lower force and highest speed is required sequential movement is more effective
What is a sentimental interaction
When a projectile is released at my maximum velocity the athlete must maximise their speed by sequential movement in sequential movement energy is transferred from across the body segments (joints) this works from the largest to slower segment working through to the faster smaller segments to ensure there is no deceleration.
Describe Bernoulli’s principle explain how it causes pressure difference and lift
It states that as velocity fluid increases the pressure of fluid the pressure the fluid exerts on the object decreases
remember we’re pressure is high velocity is low and were pressure is low velocity is high this pressure difference causes lift to occur this means that objects are forced to move from high pressure to low pressure
Defined the Magnus affect
lift force is created where in Spin is imparted on a ball when the ball spins airflow is faster on one side of the ball creating a pressure difference this is the Magnus effect or force this allows for the ball to swerve dip or saw in a direction of the spin
explain how top spin back spin and no spin effect the flight of a ball (Magnus effect)
top spin: airflow at the top of the ball is moving at a different direction to the balls spin but the airflow at the bottom of the ball is flowing at the same direction as the ball spin this area of air will accelerate causing low-pressure the ball will then move closer to the low pressure meaning that the ball Bill dip downwards decreasing the distance which the bulls travelled the force acting to pull the ball down is the Magnas force.
Backspin: the ball is forced to move upwards with the top surface of the ball which is travelling with the airflow causing it to accelerate and have low pressure the bottom of the ball is travelling in the opposite direction to the airflow causing a slow speed and a high-pressure this means that the high-pressure will move towards the low-pressure causing upward lift and the ball travel further
side spin: Side spin is created by making contact with an off centre Force on a projectile for example if you hear a volleyball to the left of the centre and follow through on the right side spin will occur the factors even greater than yourself wider
no spin: Application of a concentric force causes the ball move erratically through the air due to turbulent flow surrounding the ball. This can be further accentuated by ball design
explain top spin in relation to the most effective serve in volleyball
a server with topspin contact should be made at the bottom of the volleyball causing an eccentric force
Define laminar and turbulence flow
Laminar flow of fluid past and object with fluid flows in a continuous wind call Lea associated with low velocity objects
Turbulent flow random chaotic multi dimensional changes in momentum
what is drag state the formula and 3 things which effect drag
Drag is a fluid friction force it is the resistance of the movement and it acts in the same direction as the flow of minutes moving past the object or the opposite direction to the object the strength depends on the velocity of the movement and the size of the object and the viscosity of the fluid
total drag= pressure drag + surface drag + wave drag
define: form drag, surface drag and wave drag
pressure/form drag: in most sports is the greatest resistance is created by a pressure difference between the front and the back of the object this is affected by the cross-section of the body shape position of the body and the smooth/roughness of an object a body with a more cross-section will have a larger.
surface drag: also known as friction drag it is friction created through fluid and it is dependent on the viscosity of the fluid the magnitude of surface drag is dependent on the velocity of the body the surface area of the body on the smoothness of the body
wave drag Resistance formed by creation of waves at the point where air and waterinteract.
explain what stream singing and sip streaming
Streamlining: is making a fluid flow smoothly past an object for example how much are created to create a laminar flow to reduce the chance of air resistance being pushed in vortex pattern
sip streaming: the pressure drag increases with an increase in velocity by running in the wake or slipstream of a runner in front of you you can conserve energy.
list the factors which effect the 3 types of drag
form drag
Factors Affecting
Cross Sectional Area of object presented to the fluid – cycling upright v crouch.
Velocity of Object – higher speeds more drag
Surface Roughness – causes air to cling longer causing later separation point.
Shape of Object
surface drag
Velocity of Object
Roughness of the Object – swimmer shave down.
Viscosity of Fluid
Surface Area of the Object – size of area in contact with fluid.
Wave drag
Velocity of Wave
Technique – more streamline will reduce wave drag.
Open Water v Closed Conditions
explain what at boundary layer is and what boundary layer separation is
Thin layer of air surrounding or “attached” to the ball
Laminar (smooth flow, large turbulent pocket at back of the ball)
Turbulent (rough flow, small turbulent pocket at back of the ball)
BOUNDARY LAYER SEPARATION
Where boundary layer breaks away from ball
The earlier the boundary layer separation, the greater the pressure gradient between the front and back of the ball
Leads to ↑ drag
