Physical EducationUnit 1AREA of study 2 Biomechanical movement principles Pages 62 - 135
Work Requirements • Labs • Classwork • Homework • Participation/Attendance (80%)
Assessment Tasks • Case study analysis or data analysis • Week 4 - 5 (term 2)
What is biomechanics? • Biomechanics is the study of living things from a mechanical perspective and is essentially the physics behind human movement. • The application of the laws and principles of mechanics to living organisms. (Mechanics of Sport 1997) • The science of human movement. It applies the laws of mechanics and physics to human performance. (Live It Up 2006)
What is a biomechanist? • A scientist who is involved in: • Human performance analysis • The analysis of forces in sport and physical activities • How injuries occur in sport • Injury prevention and rehabilitative treatment methods • The design and development of sporting equipment.
What technology/equipment does a biomechanist use? • Cinematography • Computer and digital analysis • Wind tunnels • Resistance pools/swimming flumes • Electromyography
Topics we will cover: • Motion • Force production • Application of force • Newton’s three laws of motion • Momentum • Leverage • Impact and friction • Balance and stability • **Equipment design**
Inertia • The body’s resistance to change its state of motion. • Resistance to beginning movement • Resistance to changing its movement whilst moving. • The heavier an object, the greater its inertia. • Eg.
Mass & Weight • They’re different! • Mass is the amount of matter an object is made up of. Mass is usually measured in kilograms. • Weight is the force exerted on an object by gravity and is directly proportional to its mass.
Forces • “A push or a pull acting on an object.” • (from this year’s text) • “Any pushing or pulling activity that tends to alter the state of motion of a body.” • Forces on the body can be internal or external. • Examples of forces...
External Forces • Gravity • The pull towards the centre of the earth. • Friction • The rubbing of the surface of one thing against that of another. • Air resistance • The resistance against a body created by air. • Water resistance • The resistance against a body created by water.
Friction • Friction is the force that occurs whenever one body moves across another surface. • Friction always opposes motion.
Sliding Friction • Occurs when two objects slide over one another. • Eg. Rolling Friction • When an object rolls across a surface. • Eg.
Internal Forces • There are two types of internal forces: • Isometric force (without motion) • Muscular contractions create force without changing length or creating movement. • Eg. • Isotonic force (with motion) • Force is sufficient enough to change the state of motion. • Eg. • Eg.
Internal Forces • Sub-maximal force • Using a less than maximal force to create a successful, more accurate performance. • Eg. • Maximal force (force summation) • Can be achieved: • Simultaneously, where an explosive action of all body parts occurs at the same time. • Eg. • Sequentially, where body parts move in sequence. • Eg.
Lab #5 due Friday, 3rd May
Newton’s Laws of Motion • Pages 101-102 • Newton’s first law of motion • inertia • Newton’s second law of motion • Acceleration/momentum • Newton’s third law of motion • Action/reaction
Newton’s First Law of Motion: Inertia • ‘A body will remain at rest or continue in a constant state of motion unless acted upon by an external force.” • Examples...
Newton’s Second Law of Motion: Acceleration/Momentum • ‘A force applied to an object will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of the force.’ • Examples...
Newton’s Third Law of Motion: Action/Reaction • ‘For every action there is an equal and opposite reaction.’ • The total momentum of two objects before impact or contact will equal the total momentum after impact.
Momentum • “The motion possessed by a moving body.” • Momentum = mass X velocity • The greater an object’s momentum, the further it will travel and harder it is to stop. • Which has greater momentum: • A marathon runner weighs 60kg and is jogging at 10kmh. • A footballer weighs 90kg and is walking at 6kmh. (Momentum is measured in kg m/s)
An object that is not moving has zero momentum because it has no velocity • If two objects have the same mass but different velocities, the one moving quickest has the greater momentum • If two objects have the same velocity but different masses, the one with the greatest mass also has the greater momentum
Conservation of Momentum • Total momentum before a collision equals total momentum after the collision (but can be affected by external forces) • e.g. • A hockey stick is used to hit a stationary ball (zero momentum before being hit) • Before hitting the ball the stick has all of the momentum which is then transferred to the ball at point of impact (the stick still has momentum during the follow through)
Thinking things through • Page 106 • Questions 1, 2, 3, 4 & 5
Angular Momentum • The momentum of a rotating object or body. • AM = moment of inertia X angular velocity Moment Of Inertia • Is a body’s resistance to beginning rotation. • The greater the distance from the axis to the end of the body (ie. to head of tennis racquet), the greater the moment of inertia. • Moment of Inertia = mass x radius2 • Eg.