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Standard Grade PE Revision Mechanical Principles Brannock High School. When you take part in an activity, or watch someone taking part in an activity, you will see many different mechanical principles in action. These are the actions that take place to allow skills to be performed:.
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Standard Grade PE Revision Mechanical Principles Brannock High School
When you take part in an activity, or watch someone taking part in an activity, you will see many different mechanical principles in action. These are the actions that take place to allow skills to be performed: • Centre of Gravity • Transfer of Weight • Forces • Friction/Resistance • Levers
Centre of Gravity • Centre of Gravity is concerned with balance and stability. Stability depends on three things: • Height of centre of gravity • Area of Base • Centre of Gravity kept in the centre of the base Think about when you perform a Headstand in Gymnastics • Your centre of gravity is low to the ground • You have a wide base (triangle shape with head + hands) • Your centre of gravity is over your base (hips and shoulders are in line)
A B C BRAIN BUSTER Which of these gymnasts is the most stable? Why? • Gymnast A is more stable because • She has the lowest centre of gravity • She has the largest area of base • Her centre of gravity is in the centre of her base
This basketball player has transferred his body weight from his back foot to his front foot to apply more power in his pass. This gymnast, when performing a cartwheel has transferred his weight from his feet to his hands and back to his feet to generate motion in the action • Transfer of Weight Transfer of Weight involves moving your body weight from one place to another to generate power. This usually happens in throwing or hitting actions. Let’s look at some examples:
golf swing javelin throw BRAIN BUSTER badminton clear Look at the four skills below. Copy them into your jotter, and for each skill, describe, in detail how a transfer of weight takes place. cartwheel
Newton’s Third Law “For every third action, there is an equal and opposite reaction” • Forces To move forwards – you must apply force backwards To move upwards – you must apply force downwards
In the sprint start in Athletics, the sprinter will apply force backwards against the blocks. The blocks “push back” and allow her to travel forwards. In the spike in volleyball, the spiker will apply force downwards against the floor. The floor will “push back” and allow her to travel upwards. Let’s look at two examples of application of force:
BRAIN BUSTER High Jump - Fosbury Flop Swimming – backstroke start Look at the two skills below. Copy them into your jotter and describe how force is applied. Use this sentence as a guide: Force is applied____________ against___________. The direction of travel is______________.
Friction/Resistance Where there is friction there is resistance. Sometimes friction in an activity can be advantage. For example a sprinter uses friction by wearing spiked shoes. This allows him to apply maximum force to the ground and stop him slipping. At other times, friction can be a disadvantage. For example, in skiing. Skiers want to minimise friction by having smooth skies to allow them to glide smoothly over the snow.
Friction is an disadvantage in ice skating. The skaters want to minimize friction to allow them to glide freely across the ice. If there was friction, they would fall over! Friction is an advantage in Football. A Footballer wears studs to increase the friction between his boots and the ground. This stops him slipping. • Friction/Resistance
BRAIN BUSTER • Describe how the following pieces of equipment help the performer increase friction: • Spiked Running Shoes • Football Studs • Chalk • Describe how the following pieces of equipment help the performer reduce friction: • Skies • Ice Skates
In Swimming, swimmers may shave their body to reduce water resistance and allow them to travel faster through the water In Cycling, cyclists adopt a more streamlined position (low and flat to the bike) to reduce air resistance. This allows them to travel faster • Friction/Resistance Sometimes resistance can be a disadvantage and you may have to change your body position to reduce this resistance.
BRAIN BUSTER 1. Describe, in detail, how resistance is reduced in the 100m sprint
The longer the lever, the faster the speed at the end • Levers Why is the driver the longest club in the bag? Discuss with your partner. The drive is the most powerful shot in Golf and the golfer wants to hit the ball as far as possible. By using the longest club, he will generate more speed than if he used a shorter club. The greater the speed of the club head, the farther the ball will travel
In the serve in volleyball, the server uses a long straight arm to hit the ball fast, creating power in the serve. In the back flip in Gymnastics, the gymnast keeps her legs straight to increase the speed of the movement Let’s look at two other examples of when long levers play a part:
BRAIN BUSTER Tennis Serve Football Strike Hammer Throw 1. Describe, in detail, how the following athletes generate power by using long levers
worksheet 7 Section 7 – Mechanical Principles Completed To finish this section, you will be given a work sheet to complete as homework. Use your notes to help you with the answers. If you need help with a question, you can look up the Standard Grade book or ask you teacher. If you have access to the internet, you can also find help on the Bitesize website http://www.bbc.co.uk/bitesize/scotland/pe