Sport studies biomechanics

Some definitions… Velocity – speed in a given direction Acceleration – rate of change of velocity Force – a push or pull that changes the state of motion of an object Inertia – resistance to action or change Momentum – the quantity of motion that occurs

Newton’s first law of motion Law of inertia A body at rest or moving with constant velocity in a straight line, will continue in that state until a force of sufficient magnitude occurs to overcome its inertia Basically, an object will not move until you apply a force that is large enough to move it If it is moving, it will remain on that path, unless a force great enough is applied in a different direction

Newton’s second law of motion Law of acceleration This law states that the acceleration of a body is proportional to the force acting on it and that the acceleration takes place in the direction in which the force acts Basically.. the greater the applied force, the greater it’s acceleration will be This law also takes into account the fact that the accelerating effects will vary depending on the mass of the body which experiences the force Therefore.. For a greater mass, a lager amount of force is needed to provide the same acceleration

Newton’s third law of motion Law of action/reaction When on object exerts a force on a second object there is force equal in magnitude, but opposite in direction exerted by the second object on the first So.. For every action there is an equal, but opposite reaction Eg. A sprinter on the blocks experiences a force propelling him forward. As the athlete pushes backwards and downwards on the blocks, the blocks push the athlete upwards and forwards out of the blocks – ground reaction force

forces Internal forces – produced by the muscles External forces – gravity, air resistance etc. Force can… Get objects moving Stop objects moving Change the direction of a moving object Change the speed of a moving object Balance another force to keep an object still

Gravity Gravity is a constant force Gravity provides a constant force on matter, which is commonly known as weight Weight is mass multiplied by gravity Gravity causes objects to travel towards the earth at a constant rate of acceleration (10m/sec²)

Centre of gravity The centre of gravity is defined as the point around which a body’s weight is equally balanced in al directions Single segmental objects have their own centre of gravity directly above the base of support. Sometimes the centre of gravity can be outside the body (eg.Arc)

Human body centre of gravity Standing still – the centre of gravity is located in the abdominal cavity, about 6 inches above the pubis symphysis As your position changes – so does your centre of gravity The position of the centre of gravity will determine whether the body is in balance Stability and balance will be easier if: The mass is large The base is large The centre of gravity is low The centre of gravity is located over the base

Impulse Impulse is the product of the force that is applied to an object and the length of time the force is applied When a force is applied to an object, the product of the force (F) and the length of time (t) that the force is applied, is called the impulse of the force Impulse = Ft Impulse is equal to force X time, measured in Newton seconds it depends on: The time for which the force acts The size of the force applied

Momentum Refers to the quantity or amount of motion Momentum = mass X velocity

Impact The size/force applied between objects during collision The greater the momentum, the greater the impact

Frictional force Acts on the interface of surfaces which are in contact and acts in the opposite direction of motion The co-efficient of friction indicates the ease of momentum i.e. the larger the co-efficient of friction, the harder the movement is

Projectiles Height of release Angle of release Shotputters release the shot well above shoulder height, with the shot landing at ground level If the shotputter could release the shot from ground level the optimum angle of release would be at 45° Angle of release The shape of the objects flight path is dependant on the angle it is released at If ball is thrown straight up it will go directly upward and pulled straight back down by gravity If ball is thrown at an angle above 45° it will have a trajectory in which height dominates over distance

Speed of release If you throw with a faster arm action, it will go further Air resistance doesn’t really have an affect on the shotput, because it is heavy

Net force All force acting upon a body or object Ice puck example, Net force is 0 when puck is resting on surface of ice because vertical forces acting on puck cancel each other out When the hockey stick strikes the puck, an additional force is introduced, causing the puck to accelerate during the period of time the stick and puck are in contact Once contact between the puck and stick is broken, there is a zero net force situation again. Therefore, according to Newton's 1st law of motion the puck will continue to travel at a constant velocity