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Biomechanics
Chapters 3, 4, 5
| Question | Answer |
|---|---|
| Newtown's first law of inertia? | An object will remain at rest or in motion unless acted upon by an external force. |
| Newtown's second law of acceleration? | The acceleration of an object will be in the direction of the force applied and in proportion to the size of the force. F= mass x acceleration |
| Newton’s Third Law of action-reaction? | For every “action” there is an equal and opposite “reaction”. For example, action=runner pushing off blocks and reaction= opposite force from the blocks propels the runner forward. |
| Newton’s First Law of Angular Motion? | Moment of Inertia- The angular momentum of a body will remain constant at rest or in its current state of motion unless acted upon by an external toque. |
| Newton’s Second Law of Angular Motion | The acceleration of an object is directly proportional to the size of the torque applied and in the direction of the torque applied. An increase in torque is inversely proportional to the moment of inertia of the object |
| Newton's Third Law of Angular Motion | For every torque there is an equal and opposite torque |
| Linear motion | Straight/curved line, where all parts of object travel the same distance at the same time, in the same direction |
| Angular motion | Rotation around the axis can be real or imaginary . Angular motion is produced by a force that does not act throughout a body’s centre of gravity. Spin/rotation is caused when an eccentric force is applied, not through the centre of gravity of a ball. |
| General motion | Combination of angular/linear, most movements are general. Eg running the torso moves in straight line whilst arms and legs rotate or riding. |
| Projectile motion | Flight of an airborne object |
| Inertia definition | A body's reluctance to change its state of motion whether it is in motion or at rest. Inertia is directly related to the mass of an object. |
| Moment of inertia - Definition + formula | Moment of inertia= Mass x Radius^2. Is a measure of an object’s reluctance to rotate. A tennis racquet’s moment of inertia will be determined by its mass and length |
| Mass and weight | Mass is the amount of matter an object is made up of (kg). Weight is the measure of gravitational force acting on the mass. |
| Force - Formula + Definition | Force= mass x acceleration. Is a push or pull which changes state of motion. Forces can change the shape of an object or move an object. Forces can either be internal (muscular contractions) or external (outside sources) |
| Torque - Formula + Definition | Torque= Force x Lever arm. A measure of the turning effect and is dependent on the force applied and the distance from the axis it is applied. Torque is dependent on the size of the applied force and the length of lever/moment arm. |
| Impulse - Formula + Definition | Impulse= Force x Time. The change in momentum of a body (greater impulse=greater momentum). Greatest changes of momentum will occur when maximum forces are applied for as long as possible |
| Forces opposing motion | Gravity, Air resistance, Fluid resistance and friction. |
| Gravity | Pull the object back to earth and constant force accelerates the object at 9.8 ms2. Gravity holds stationary objects in place and it creates objects parabolic flight path |
| Air resistance | Creates disturbance in flow causing drag force. Air around an object and acts in opposite direction and slows horizontal velocity reducing distance traveled. AR dependent on: Shape of an object Cross sectional area of object Velocity of the object |
| Fluid Resistance | Creates disturbance in flow causing drag force. Flow of water around an object, when swimmer move through water they create turbulence. FR reduced by: Shaving body hair Swim caps/Tight clothes Adopting a streamlined body position (arrow) |
| Friction | Force that opposes motion when two surfaces are in contact with each other. Friction must be overcome to move an object. |
| Types of friction | Sliding Friction and Rolling friction |
| Sliding Friction | Reduces friction by using waxes and polishes. In other sports athletes use spikes or blades to reduce sliding friction. |
| Rolling Friction | An object rolling across a surface will be dependent on the surface of the object and the surface the object rolls across, radius of object (bigger= greater surface contact increasing friction), weight of object (friction is proportional to weight). |
| Linear momentum - Defintion + Formula | Momentum= Mass x Velocity. When two objects collide a change in momentum occurs and the objects will generally move in the direction of the object with greater momentum. Objects with greater momentum have greater inertia |
| Conservation of momentum | The total momentum of objects before a collision is equal to the total momentum of the objects after the collision therefore conserving. |
| Summation of momentum | Force summation is a vital ingredient of human movement where the correct timing and sequencing of body segments and muscles through a range of motion is evident. |
| Simultaneous summation of momentum | Involves all body parts acting together at the same time to generate force, running |
| Sequential summation of momentum | Involves all body parts contributing in sequence to generate force, golf drive |
| To maximise summation of movement. | -Use as many body parts as possible (impulse) -Start with heavier, slower body parts and move through to lighter, faster body parts -Timing -Follow through to prevent unnecessary deceleration |
| Angular momentum - Definition + Formula | Angular momentum= Angular Velocity x Moment of Inertia. Is a product of moment of inertia and angular velocity. |
| Conservation of Angular Momentum. | Once airborne, angular momentum cannot be altered. A decrease in moment of inertia will be met with an increase in angular velocity. Eg. Diver changing position from straight to tuck. |
| Angular distance | Is the total of all angular changes of a body or object in degrees |
| Angular displacement | How far from the starting/initial position of a body/object to the final angular position in degrees |
| Speed | Speed=Distance/Time. How much distance covered in a period of time. |
| Angular Speed | Angular speed=angular distance/time. How much distance covered in a period of time. |
| Velocity | Velocity=Displacement/Time. Is the time taken to change position it has both a magnitude and direction. |
| Angular velocity | Angular velocity= Angular displacement/Time . How quickly an object is spinning around its axis |
| Acceleration | Acceleration= Change in velocity/time. Can be positive, increasing speed, negative, decreasing speed or zero(constant velocity or stationary.) |
| Angular Acceleration | Angular acceleration=Change in angular velocity/time. |
| Projectile motion | When an object becomes airborne it becomes a projectile |
| Factors affecting projectile motion. | Height of release, Angle of release and Velocity of release. |
| Equilibrium | Is where no unbalanced forces or torque are acting, this can be whilst moving, stationary (static equilibrium), or at a constant speed (dynamic equilibrium), but not when accelerating. |
| Balance | Is the ability to maintain and control equilibrium |
| Stability | The ability to resist change, or disruption to equilibrium. In sports athletes manipulate stability in order to improve performance. |
| Factors that influence stability | Height/alignment of centre of gravity, Friction, Mass, Area of base support, Velocity |
| Centre of gravity | Point of balance of an object where weight is evenly distributed. It is located inside the pelvis and is slightly higher in males and varies with body position. When the line of gravity falls outside the base of support stability will be lost. |
| Base of support | The bigger area of the supporting base the greater the stability, this allows the centre of gravity to move more before falling out of the base of support. |
| Friction in terms of stability | Greater friction and contact surface area will result in greater stability. For example wax on a surfboard, athletes' spikes. |
| Mass in terms of stability | Greater mass= Greater inertia and ability to resist forces making it more stable |
| Levers | A rigid structure or beam that rotates around an axis. Levers are made up of 3 components. Force , Axis and Resistance. Type of lever can be determined by 1,2,3 A-R-F |
| First class levers | Axis (fulcrum) is between force and resistance (moving head). Either =1, >1, <1 |
| Second class levers | Resistance is in between axis and force (Calf raise). Always >1 |
| Third class levers | Force is in between axis and resistance (Kicking ball). Always <1. Mostly common in the human body. |
| Mechanical Advantage | Mechanical advantage= force arm/resistance arm. |
| When Mechanical Advantage is < 1 | The force required to move the load is greater than the force of the resistance. More effort is required to move the resistance, however velocity will be much greater. |
| When Mechanical Advantage is > 1 | If the mechanical advantage of a lever is greater than 1, the force required to move the load is less than the force of the resistance (less effort). |
| QMA Principles | Qualitative movement analysis principles (preparation, observation, evaluation and error correction) |
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Campbell_McClounan
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