# Performance Analysis and Evaluation of Health Status- Biomechanics

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• Created by: dsmeikle
• Created on: 27-12-16 13:07
What is balance?
Balance is holding your body weight and centre of gravity over or through your base of support.
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How is balance achieved?
A low centre of gravity and a big base. Example: plant both feet wide and stand up straight.
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What is your base of support?
The area which is covered by the parts of your body which are touching the ground.
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What is your centre of gravity?
Your body's point of balance. It's close to your belly button. It is the average location of the weight go an object. If you put your centre of gravity outside your base of support, you lose your balance.
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What is 'body tension'?
When you hold your balance you tighten the muscles in your body.
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What is an axis of rotation?
An imaginary line about which the body rotates or spins at right angles to the plane.
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What is the longitudinal axis?
It runs from the top to the bottom of your body. Example: When a gymnast performs a 360 degree turn, they're rotating around the vertical axis.
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What is the transverse axis?
It runs from side to side of the body. Example: a somersault is a rotation through the transverse axis.
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What is the sagittal axis?
It runs from the front to back of your body. Example: when a gymnast performs a cartwheel they have rotated around the sagittal axis.
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How do you increase the speed of rotation?
Bring your body as close to the axis of rotation as possible. Example: Gymnasts tuck in tight to rotate quickly.
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How do you slow down the speed of rotation?
Move more of your body away from the axis of rotation.
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How is the transfer of weight is used to allow you to move your body weight in any direction?
You must apply a force in the opposite direction. The force is created when you contract your muscles. When this happens against a resisi
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What is Friction?
When two surfaces rub together leading to an increase in resistance.
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Advantage: footballers wear studs to increase the friction between their boots and the ground to allow them to stop or change direction quickly.
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Disadvantage: air resistance in cycling can slow you down. Cyclists wear tight clothes to reduce friction and increase their speed.
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What is streamlining?
Swimmers overcome the resistance of water using streamlined body position. To streamline the body the swimmer would put their body into a share or position, which offers the smallest surface area and the least resistance.
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In striking/kicking/throwing actions the part of the body or piece of equipment continues after the object has been struck or released.
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What is the purpose of follow through?
It allows you to get more power and accuracy into a throw. It also keeps the player balanced and can prevent injury.
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What is a plane?
An imaginary flat surface through the body.
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What is the frontal plane?
Divides the body into the front and back. Movements in the frontal plane rotate around the sagittal axis e.g. a cartwheel.
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What is the sagittal plane?
Divides the body into left and right. Movements in the sagittal plane rotate around the transverse axis e.g. somersaults.
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What is the transverse plane?
Divides the body into upper and lower segments. Movements in the transverse plane rotate around the longitudinal axis e.g. spinning skater.
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What is a lever?
A means of applying force at a distance from the source of the force.
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What are the three components of a lever?
A fulcrum (pivot), effort and load.
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What is a first order lever?
A see-saw lever e.g. triceps/elbow (rarely found in the body). The pivot is between the effort and the load.
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What is a second order lever?
The load is between the pivot and the effort (wheel barrow). Mechanical advantage.
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What is a third order lever?
The effort is between the pivot and the load. Mechanical disadvantage (effort needs to be bigger than the load). Most common in the body e.g. quads/knee.
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What example can be given of a third order lever being used in sport?
The fulcrum is the knee joint, the load is the weight of the ball plus the lower leg and the effort is the force applied to the quads as it contracts to pull the lower leg.
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What is Newton's first law? (The law of Inertia)
A body continues in a state rest or uniform velocity unless acted upon by an external force.
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What is Newton's second law? (Law of acceleration)
When a force acts on an object, the rate of change of momentum experience by the object is proportional to the size of the force and takes place in the direction in which the force acts.
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What is Newton's third law? (F=MxA)
'For every action there is an equal and opposite reaction'.
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What is weight?
A force caused by gravity measured in newtons. The weight of an object is the gravitational force between the object and the Earth.
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What is mass?
The amount of matter. Measured in Kg.
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What is inertia?
The property of mass which means that it is hard to get a massive body moving, and also hard to stop a it when moving, Related to newton's first law. Measure in Kg. The smaller the moment of inertia, the faster you spin.
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What are 'moments'?
Turning forces around a pivot. Moment= force x distance.
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What is momentum?
Mass on the move. A concept derived from newton's second law. Force= rate of change of momentum. Momentum= mass velocity.
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What are impulses?
Impulse= total change of momentum = force x time. Derived from newton's second law. Useful when large forces are applied for a short time e.g. kicking a ball.
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What is a parabola?
The flight curve of objects thrown if there is no air resistance.
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What is fluid friction?
Applied to objects moving through fluids (gases or liquids). It is the force that acts in the opposite direction to the direction of motion.
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What does fluid friction depend on?
The size, shape and speed of the object. Also, streamlining.
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How does streamlining help reduce fluid friction?
It assist with laminar flow. A cyclist for example travels much faster than a runner therefore they experience high levels of fluid friction. He or she crouches low to reduce forward cross section and helmet is designed to minimise turbulent flow.
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What is the Magnus Effect?
Spinning balls generate a lift force produces as a result of the manis effect, which explains the curved light of a ball. The spinning surfaces effect airflow around the ball.
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What is drag?
As an object moves through the air, the air resists the motion and the resistance force is called drag. Drag is directed along and opposed to the flight direction.
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What factors affect the magnitude of the drag force?
Shape and size of the object, the square of the velocity of the object and the density and viscosity of the air.
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What is lift?
The component of the aerodynamic force that is perpendicular to the flight direction.
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What factors affect the magnitude of the lift?
Conditions of the air and object, the velocity between the object and air and the speed and direction of rotation
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What 3 things affect the distance travelled by a projectile?
1) Angle of release. 2) Height of release. 3) Speed of release.
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What is the Bernoulli effect?
The effect that enables aerofoils (wings) to fly. (Example in sport: Inverted wings on race cars used to create down-force which increases friction for cornering).
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What factors cause the Bernoulli effect?
The reduction in pressure on a surface across which a fluid moves. The greater the speed of the fluid, the bigger the pressure difference, the greater the force.
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How do you apply spin on a ball? (the Magnus effect is the Bernoulli effect applied to spinning balls).
Striking a ball creates high pressure. If the high pressure is on the top if the ball top spin will occur and the ball will move down. If you hit the ball at the bottom, the high pressure is underneath causing lift and back spin, the ball moves up.
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What is centre of mass?
The scientific term for centre of gravity. It is the single point in a body which represents all the spread out mass of a body.
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## Other cards in this set

### Card 2

#### Front

How is balance achieved?

#### Back

A low centre of gravity and a big base. Example: plant both feet wide and stand up straight.

### Card 3

#### Front

What is your base of support?

### Card 4

#### Front

What is your centre of gravity?

### Card 5

#### Front

What is 'body tension'?