Module 2562 A.2.1 FORCE FORCE is push or pull the unit is the NEWTON (10 N is approx the weight of 1 kg) force changes the state of motion of an object force causes acceleration or deceleration or change of direction the more force the bigger the acceleration force changes the shape of an object WEIGHT FRICTION REACTION FORCES AIR RESISTANCE / FLUID FRICTION – all these forces affect the sportsperson Motion and Movement - Newton’s Laws

Module 2562 A.2.2 NEWTON’S FIRST LAW of MOTION NEWTON’S FIRST LAW this law is used when ZERO NET FORCE is applied to an object this doesn’t mean that zero force acts, but that all forces MUST CANCEL OUT with zero net force an object – is STATIONARY or – moves at CONSTANT SPEED in the SAME DIRECTION a sprinter in full stride has four forces acting but they cancel out exactly therefore he / she travels at constant speed Motion and Movement - Newton’s Laws

Module 2562 A.2.3 NEWTON’S SECOND LAW of MOTION NEWTON’S SECOND LAW this law is used when a NET FORCE acts on an object net force FORWARDS produces ACCELERATION net force BACKWARDS produces DECELERATION net force SIDEWAYS produces CHANGE OF DIRECTION the bigger the force the bigger the acceleration the sprinter slows down at the end of a race there is a net force backwards so the sprinter decelerates Motion and Movement - Newton’s Laws

Module 2562 A.2.4 NEWTON’S THIRD LAW of MOTION NEWTON’S THIRD LAW this law is used when two bodies EXERT FORCES ON ONE ANOTHER ACTION AND REACTION ARE EQUAL and OPPOSITE IN DIRECTION action of jumper down on ground = reaction of ground up on jumper the harder you push down on the ground, the more the ground pushes up on you this upward force on the jumper is the force acting to cause the take off Motion and Movement - Newton’s Laws

Module 2562 A.2.5 The EFFECTS of FORCE EFFECTS of FORCE force causes linear acceleration or deceleration including change of direction the point of action of a force affects what happens friction acts at the feet of a sportsperson, not enough of it and the person’s feet slip if a force acts through the person’s centre of mass (CofM), then linear motion is caused if a force acts to one side of the CoM then rotation is caused like take-off in the high jump, the reaction force acts to one side of the CoM Motion and Movement - The Effects of Force

Module 2562 A.2.6 CENTRE OF MASS CENTRE of MASS (CoM) this is the single point in a body which represents all the spread out mass of a body the weight acts at the CoM since gravity acts on mass to produce weight Motion and Movement - Centre of Mass

Module 2562 A.2.7 CENTRE OF MASS WHERE IS THE CENTRE OF MASS? position of centre of mass depends on shape of body this is how the high jumper can have his CoM pass under the bar but he could still clear the bar Motion and Movement - Centre of Mass BALANCE to keep on balance the CoM must be over the base of support

Module 2562 A.2.8 INTERNAL FORCES and LEVERS LEVERS a lever is a means of applying force at a distance from the source of the force Motion and Movement - Levers INTERNAL FORCES this describes the forces acting when a muscle pulls on its origin and insertion the force on the origin H is equal in size but opposite in direction to the force on the insertion U this changes the shape of the person a lever has a FULCRUM (pivot), EFFORT and LOAD in the human body, usually a joint and the attached limbs or bones act as a lever FORCE is applied as effort by a muscle or group of muscles the LOAD is the force applied to the surroundings by the lever

Module 2562 A.2.9 LEVERS EFFECTS OF THE LENGTH OF LEVER the length of the lever (d in the diagram) affects the load able to be exerted by the lever, and the speed at which the hand can move the longer the lever d, the smaller the value of the load for a given biceps strength the longer the lever arm d, the faster the load can be applied (as the limb moves through its range - a longer limb - the hand - would move further in the same time) EFFECTS OF THE ANGLE BETWEEN EFFORT AND LEVER ARM the effect of the effort is affected by the angle between the direction of the effort and the lever arm optimum load is exerted when this angle is 90 o Motion and Movement - Levers

Module 2562 A.2.10 EXAMPLES OF LEVERS Motion and Movement - Levers TRICEPS ELBOW LEVER class 1 lever : pivot between effort and load see-saw lever found rarely in the body CALF MUSCLES / ANKLE LEVER class 2 lever : load between pivot and effort wheelbarrow lever, load bigger than effort QUADS KNEE LEVER class 3 lever : effort between pivot and load mechanical disadvantage, effort bigger than load, most common system found in body another example : biceps / elbow