Biomechanics Revision Flashcards
What is biomechanics?
Study of living things from a mechanical perspective like forces and motions
What do biomechanics do?
They study how the athlete does things and interacts with their environment and then uses it to improve the athlete’s conditions and help prevent injuries
What is biomechanical movement analysis?
Measurements - quantitative and qualitative
What are quantitave and qualitative variables?
Quantitative - kinetic (forces) and kinematic (motion : distance, speed, acceleration)
Qualitative- descriptive e.g “push with more force”
Measurement tools for biM movement analysis?
- Video analysis for repeat viewing, slo-mo
- optoelectronic motion analysis (reflective balls on suit)
- accelerometer for speed and acceleration of body
- electromyography for recording electrical activity in muscles before contractions
- force platform for standing on
- goniometer for measuring joint angles
What is force and how is it measured?
Force causes objects to accelerate and is measured in Newtons (N) and is calculated by (F=m times a) m- mass a-acceleration
What is a vector quantity?
Depends on direction, magnitude and point of application
What are the 4 types of forces?
External - gravity, wind, objects, people
Internal - muscles, bones, connective tissues
Motion - angular, curvilinear
Reactionary - ground, joint
What is gravity? And how do you calculate it?
Is a constant force that pulls through an object’s centre of mass towards the earth
Weight force - mass times gravity
Acceleration due to gravity is 9.8m/s^2
What is friction and what affects it? And how do you overcome it?
Friction opposes the motion of an object and occurs when 2 surfaces come in contact with each other.
It is affected by nature of the 2 surfaces and the force pressing them together
Maximum amount of friction = maximum static friction
To overcome it, you must apply an increasing greater force
How is friction used in sports?
By increasing (more grip like using footwear, chalk to increase friction between hands and bar)
And decreasing (skiing)
What is air and water resistance and what affects it?
When going through water or air - it becomes drag
It’s affected by air density , cross sectional area of body, speed of body (incr. Speed = more drag)
Drag is a type if friction
How is it used in sports?
Full-bodied swim/body suits for high speed sports
What is force summation? How can you improve it?
The sum of all forces generated by each body part
Utilising more body part/muscle
Improving rom
Correct sequencing body parts
Improving coordination and timing of body movements
What types of force summation?
Simultaneous force summation - body parts moved at the same time (deadlifts)
Sequential force summation - in a sequence (for maximal force) “” big body - wide bos - other parts
What is motion and types of motion?
Motion is a movement that results from a force
Linear motion - go in straight line over same distance
Curvilinear motion - is curved
Angular motion - rotates on a central axis (axis of rotation - real or not, internal or external)
General motion - Angular + linear motion
What are newton’s laws?
1st law - inertia (an object will continue at that state unless a force that’s strong enough is acted upon it) (ball won’t move unless kicked)
2nd law - law of acceleration (acc. of object is proportionate to the appl. force in the direction it applied to)volleyball pass
3rd law - action and reaction (for every action, there’s an equal and opposite reaction) runner pushing against ground
How to measure motion?
Speed, velocity, acceleration, momentum, impulse, torque
Motion = only when moving
Formula for newton’s second law
F = m x a
Tucked in means
Low moment of inertia and high Angular velocity
Lever classes?
F, L, E = 1,2,3
Therefore
1st = EFL (see-saw)
2nd = FLE (toes, wheelbarrow)
3rd = FEL (fishing, lifting)
Measuring motions - speed, velocity, momentum, impulse, torque
Speed (kms/hour) only distance/time
Velocity (displacement/time) displacement = distance from start
Acceleration (v/t^2) change in velocity (metres/second squared) - producing power
Momentum (mass x velocity) application of inertia
Impulse (force x time) equal to the change in momentum of object
Torque (force x lever arm) Angular motion by a eccentric force
What happens in torque?
Spins a ball using eccentric force
If through the centre of gravity = no spin
If not through “” = spin
What is mechanical advantage?
The efficiency of a lever. The greater the MA, the less effort is needed. It can be less than 1 or greater than 1. Longer arm means more movement (golf club)
How to calculate mechanical advantage?
Force arm / resistance arm
Force arm = fulcrum to effort distance
Resistance arm = distance from resistance to the load
What is equilibrium and other factors like balance, stability, dynamic, static?
Equilibrium - an object where the opposing forces are balanced and equal.
Balance - ability to control equilibrium
Stability - resistance to disruption of equilibrium
Dynamic equilibrium - object moving with a constant velocity and no change in speed or direction
Static - all forces on object = 0, all torques = 0. Standing in water isn’t static
Stability and balance in sports
Stability - Swimming = decrease stability to jump into water
Running = “” push off blocks
Wrestler - increased stability to not be pushed
Balance - Gymnast - good balance to maintain position after performing
What affects stability?
Base of support, CoG, body mass (to find cog), friction (btwn body and surface), line of gravity (cog to ground)
What is projectile motion?
When an object in the air is affected by gravity and air resistance
What is trajectory and what are its components?
It’s the path of a projectile. And is composed of vertical and horizontal (e.g high jump = vertical and discus = horizontal)
Vertical - gravity and initial vertical velocity
Horizontal - distance
Initial vertical velocity - force applied at beginning
What affects vertical and horizontal components?
Vertical - gravity causes its ivv to be negative
Horizontal - drag but not air resistance
How does it affect the trajectory? What is the optimal angle of release?
Speed of release, angle of release: ground = more over 45° and vertical = 90°
Parabolic = ball
If height is 0, then oar is 45°
Magnificent affect?
Difference in pressure as ball in air, with or without spin
Creates pressure on both sides of object.
Backspin - spins in direction it came from. Lower pressure
Faster air = lower pressure (more air under ball)
slower air = more pressure
Topspin - in direction it’s going to. Higher pressure
What is the coefficient of restitution? How is it measured?
A value between 0 and 5 that describes the elasticity of an object
Elasticity - how well an object regains it’s original shape after being hit
The greater the cor, the more elastic it it.
It is measured by square root of height bounced over height dropped from
What affects cor?
Nature of ball (leather, metal, rubber.. rubber is more elastic)
Temperature of ball (warmer means more elasticity)
Nature of surface (hard surface = more force onto ball = bouncier than clay)
Nature of striking implement (metal bat = more energy absorption than wooden bats)
Velocity of impact (harder hit = greater compression) without elasticity a ball will shatter
Angles of approach for Topspin and backspin?
Topspin - sharper angle of incident but shallower angle of approach
Backspin - shallower angle of incident but sharper angle of approach
Accuracy and how to improve?
How well you can direct object towards intended area and precision is how well you can continue your accuracy
To improve accuracy, flatten the curve so it gives more time to control it in the right direction
