Standard Grade Knowledge & Understanding

Standard Grade Knowledge & Understanding Skills & Techniques - Mechanical Principles • Balance • Axis of Rotation • Transfer of Weight • Force • Resistance • Friction • Propulsion • Levers

Balance • Balance is the ability to retain the centre of gravity over your base of support. • Balance – The ability to remain balanced depends on 2 things: • A) Base of Support • B) Centre of Gravity • If your base of support is large your balance will be more stable • If your base of support is small, it is harder to keep your balance

Balance • To remain balanced for a period of time, you have to tighten the muscles in your body – this is called body tension • The exact muscle requirements depend upon the nature of the task. • Static balances such as headstand in gymnastics require you to hold a balance • Dynamic balances require you to maintain balance under constantly changing conditions. When skiing you constantly adjust your dynamic balance as you travel over changing terrain in order to remain balance Static Dynamic

Centre of Gravity • Centre of Gravity – is your point of balance. When standing upright it is near your belly button • If your centre of gravity is low you will balance more easily • If you move your centre of gravity outside your base of support, you will lose your balance.

Good balance is very important to be successful in lots of activities: A large base allows the golfer to be balanced in preparation for his swing Having his centre of gravity over his base allows the footballer to be balanced during his shooting action A low centre of gravity allows a volleyball player to remain balanced when performing a dig

Axis of Rotation • There are 3 axis of rotation: • Vertical Axis – top to bottom (ie – Full turn jump) • Transverse Axis – side to side (ie – front somersault, backwards roll) • Antero Posterior Axis – front to back (ie – cartwheel) Vertical Antero Posterior Transverse

Axis of Rotation • The speed of rotation depends on your body shape • If your body shape is close to the axis you will rotate more quickly • If your body shape is further away from your axis you will rotate more slowly • Eg – An ice skater will tuck his body into a tight ball in order to spin round fast, then extend his arms and body out wide when he wants to slow down. • Can you give an example from you Standard Grade Course where you used this principle to help with your performance of a skill?

Transfer of Weight • Transfer of weight is very important in physical activities. It allows you to move your body from one place to another • To transfer your weight, a force must be applied in the opposite direction. Force is created by the contraction of muscles In order for the volleyball player to transfer his weight upwards he must push down hard on the court

Transfer of Weight • Transferring weight is also important in activities where an object has to be struck with power By transferring his weight forward the softball player can exert a greater force on the ball, thus hitting it further From your course describe one technique which requires a single transference of weight? From your course describe one technique which requires a repeated transference of weight?

Resistance • In some activities resistance can be a disadvantage (it may hold you back) • For example cyclists wear tight lycra clothing, which helps reduce air resistance, and lets them cycle faster • A specially designed helmet and curved body position also helps to reduce air resistance

Resistance – Tasks • For the different activities in your Standard Grade course, describe one technique where resistance has helped your performance? • For the different activities in your Standard Grade course, describe one technique where resistance has made your performance more difficult? • For the different activities in your Standard Grade course, describe one technique where improved streamlining has limited the effects of resistance?

Friction • When two surfaces touch friction occurs. • In football, players wear boots with studs. • This enables them to grip the ground better, helping them to turn quickly. • If a player used flat soled trainers, the lack of friction between the shoe and the ground would result in the player slipping when turning.

Propulsion • Propulsion is the movement of an object through water • In rowing, oars are used to pull the water back, thus propelling the boat forwards • In swimming, arms and legs act in a similar way. They force the water back, pushing the body forwards. The faster and stronger the pull, the faster the swimmer will go • By keeping a streamlined shape in the water (long thin shape), a swimmer can move faster due to reduced water resistance • Competitive swimmers sometimes shave their legs and arms in a bid to reduce water resistance even further

Levers • Levers can be used to create more power in physical activities. • The longer the lever used, the more power gained • In tennis, a player will extend her arm and the racquet in order to hit the ball more powerfully. This is best demonstrated with the serve • In softball, a player will hold the bat at the bottom, creating a long lever. This allows him to produce a much more powerful hit • In football, a player will shoot using the whole of the leg. By making a long lever with the leg, more power can be transferred to the shot. Long levers

Levers • Short levers are also important in some activities. By using a short lever, the performer can gain more accuracy and control • For example, in football some players choose to shoot with the inside of the foot. Given that the lever used for this skill is shorter (knee to foot), less power but more accuracy can be obtained

Standard Grade Knowledge & Understanding