OCR AS Physical Education ANATOMY AND PHYSIOLOGY Basic Concepts of Biomechanics ‘Forces’

Summary of facts In order to move our body to carry out sporting techniques, any movement (motion) is produced by force. The force has to be large enough to overcome our moment of inertia If the application of force is great enough the resultant change in position of a body’s centre of mass from a stable to unstable positions will cause motion in sport. All motion is governed by Newton’s 3 Laws of motion

Key Terms Body: Body: this describes ANYTHING a human being or object Force: Force: often described as the push or pull on a ‘body’. Inertia: Inertia: the resistance a ‘body’ has to a change in its state of motion. REMEMBER: for a body to move, the force that acts on it must be large enough to overcome the inertia of the body. We must also consider the direction of application and the position of application

A force can have the following NET effects: 1.It can cause a body at rest to move 2.It cause a moving body to change - Direction - Speed (Accelerate/Decelerate) 3. It can change an objects shape

Effect of ForceDescription of Penalty Kick in Football A force can cause a body at rest to move The football will remain at rest on the penalty spot until the force of the footballers boot causes it to move. A force can cause a moving body to change direction 1. 2.Consider the penalty taker when they are approaching the ball. After initially starting to move, he can accelerate towards the ball by applying a larger force on the ground A force can cause a moving body to decelerate 3. A force can cause a body to change its shape At the point where the players boot contacts the ball, the ball will be slightly deformed & no longer truly spherical. Also, the force of the ball on the net will cause the net to change shape.

Anatomy & Physiology: AS PE A body at rest to move A moving body to change direction Change its shape DecelerateAccelerate A snooker ball will remain on the table until it is struck with a snooker cue. In tennis, the direction of the ball struck by a forehand drive will change as the opponent strikes the ball to return it over the net. When a trampolinist lands on the trampoline bed, the bed changes shape. When the fielder catches the ball in rounders the flight of the ball is stopped. As the long jumper gets to the end of their run-up they apply more force on the ground to accelerate into the final few strides before hitting the board.

What are the APPLICATION effects of a Force? LETS REMEMBER: The effect of a force will depend on its application; Size Size of the force Direction Direction of the force Apply Where you Apply the force (Position in relation to the CoM)

RECAP NEWTONS LAWS Newton’s 1 st Law of Motion The Law of Inertia ‘A body continues in a state of rest or uniform velocity unless acted upon by an external force’.

Newton’s 2 nd Law of Motion The Law of Acceleration “When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force & takes place in the direction in which the force acts”

Newton’s 3 rd Law of Motion The Law of Reaction “When an object exerts a force on another, there will be an equal & opposite reaction exerted by the second on the first”

RECAP MOTION Linear Motion: “When a body moves in a straight line or curved line, with all its parts moving the same distance, in the same direction & at the same speed” Angular Motion: “When a body or body part moves in a circle or part circle about a fixed point called the axis of rotation” General Motion: “A combination of linear & angular motion”

Bobsleigh Cycling Gymnastics Which motion is which?

Linear Motion - Examples Motion along a line, including a performer sitting in a toboggan & travelling straight down a hill or a curved line followed by a performer lying in the skeleton bob event as they slide around the corners of the downhill track. The flight path followed by the shot put after the point of release is another example of linear motion in a curved line.

Angular Motion - Examples When we apply this concept to the human body we often talk of athletes spinning, circling, turning & somersaulting. An example is the circles produced by a gymnast on the uneven or high bars. During one stroke cycle of the front crawl the arm moves a complete circle about an axis of rotation: the shoulder joint.

General Motion - Examples The approach run up of a javelin thrower shows general motion as the javelin & torso are showing linear motion by moving in a straight line. However, the arms & legs of the athlete are showing angular motion as the non-throwing arm rotates around part of a circle about the shoulder joint, the upper legs about the hip joints, the lower legs about the knee joints & the feet about the ankle joint.

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