KEY KNOWLEDGEKEY SKILLS  Linear motion occurring in sport and physical activities from the perspective of acceleration and deceleration and both velocity and distance/displacement  Angular motion occurring in sport and physical activities by considering torque, angular velocity, momentum and moment of inertia.  Correct use of terms that explain how biomechanical principles apply to a range of sporting movements  Investigate and interpret graphs of biomechanical principles pertaining to movements in sports and activities  Participate in, analyse and report on a range of biomechanical activities  Evaluate the efficiency of various movements by applying biomechanical principles  Compare and contrast a variety of sports movements and discuss the correct way biomechanical principles can be used to bring about improvements. © Cengage Learning Australia 2011

Biomechanics is the study of living things from a mechanical perspective and is essentially the physics behind human movement. Biomechanists are responsible for:  Human performance analysis (see next slide)  The analysis of force in sport and physical activities  How injuries occur in sport  Injury prevention and rehabilitative treatment and methods  The design and development of sporting equipment. © Cengage Learning Australia 2011

Motion © Cengage Learning Australia 2011

There are 3 basic forms of motion: LLinear motion  Angular motion GGeneral motion.

Linear motion:  Linear motion occurs when all the parts of an object travel over the same distance at the same time. E.g. Ice-skater gliding down the ice.

Curvilinear Motion:  When a curved line is evident  The flight or trajectory of a projectile is usually in a curvilinear motion  E.g. Throwing a javelin or a long jumper

Angular motion:  Angular motion is evident when the body or an object turns about an axis of rotation.  The axis may be a fixed point – for example, the shoulder joint in a throw.  In the human body the body parts closest to the axis of rotation move less distance than do the body parts furthest from the axis of rotation.

General motion:  Angular motion tends to be far more common in sports than linear motion. However most sporting activities use a combination 0f both – linear and angular motion.

General motion:  General motion may be described as linear motion of the whole body that is achieved by the angular motion of some parts of the body.  E.g.1) 100m sprint – the whole body moves in a straight line as a result of the angular motion of the legs about the hip joint.  E.g.2) A cyclist pedalling and a kayaker paddling down the river.

Distance is the path travelled from start to finish, regardless of direction. Displacement is defined as a change in position. © Cengage Learning Australia 2011

1.Calculate the speed of a car if it travels 100 metres in 5 seconds. Speed can be calculated by dividing the distance travelled by the time it took Velocity is equal to the time it takes to change position Both are expressed as metres per second or m/s © Cengage Learning Australia 2011

Acceleration is the change in velocity over a period of time and when positive an object is speeding up and when negative it is slowing down. Something with zero acceleration is simply not changing its velocity and could be moving at a constant velocity. Expressed as m/s ² © Cengage Learning Australia 2011

This involves rotation around a central axis or point (real or imaginary) You can see these angular motions allow the body to move in a linear way. Angular motion © Cengage Learning Australia 2011

Angular motion is caused by a force acting outside the centre of gravity – this is known as an eccentric force and results in rotation known as torque. Torque is sometimes referred to as moment of force Moment of force = force x lever arm The greater the torque, the greater the rotation/angular acceleration. Torque © Cengage Learning Australia 2011

Torque is affected by: length of level arm amount of force applied Spin is a classic example of torque. The bigger the lever arm and the greater the applied force = the greater the amount of spin of an object. © Cengage Learning Australia 2011

Angular distance = the angular distance covered by a rotating body, e.g. a gymnast doing two full rotations on the high bar would cover 360 ° x 2 = 720 ° Angular displacement = the change between the initial and final position of a rotating object, e.g. a gymnast doing a one and a half rotation on the high bar would displace only 180 ° even though they have covered 360° + 180° = 540°. © Cengage Learning Australia 2011

Angular speed = angular distance covered ÷ time taken to complete rotation, e.g. a gymnast doing two full rotations in 2 seconds on the high bar would cover 360 º x 2 = 720º ÷ 2 = 360º / second Angular velocity = the rate of change of angular displacement, e.g. a gymnast doing a one and a half rotation in 1 second on the high bar would displace only 180º ÷ 1 = 180º / second Angular acceleration = the rate of change of angular velocity or the rate of change in angular velocity – this can be positive or negative (deceleration). Angular speed, velocity & acceleration © Cengage Learning Australia 2011