PE Biomechanics Biomechanics investigates the internal and external

PE - Biomechanics

Biomechanics investigates the internal and external forces acting upon a body. – Forces include: Gravity Mass friction Inertia Muscle action

Components of biomechanics Motion Balance and Stability Force Fluid mechanics

Today we’ll look at… Newtons laws 1, 2, 3 Forces and what they can do? Centre of mass and stability Types of motion

Motion is the description of the change of position of an athlete or an implement.

Newton’s Laws of Motion Three Laws – 1 st Law – Inertia – 2 nd Law – Acceleration – 3 rd Law – Action and Reaction

Newton’s First Law of Motion A body continues in a state of rest or uniform velocity unless acted upon by an external force. Sporting Examples: “ A football will stay on the penalty spot until kicked” “A hockey ball will remain still until hit by the stick” “ A football will roll until slowed by friction or another player” “ A hockey ball will not fall from the air without the application of gravity”

Newton’s First Law of Motion A body continues in a state of rest or uniform velocity unless acted upon by an external force.

Newton’s First Law of Motion A body continues in a state of rest or uniform velocity unless acted upon by an external force. PUSH or PULLS can alter a body (object) in the following ways • Cause a body to move (as seen in the previous slide) • Cause a body to accelerate • Cause a body to decelerate • Cause a body to change direction • Cause a body to change shape

Forces Can Cause a body to accelerate Sporting example: Sailing boat. The force that causes the boat to acceleration is the wind.

Forces Can Cause a body to decelerate Sporting example: Sailing boat. The force that causes the boat to deceleration is the wind.

Forces Can Cause a body to change direction Sporting example: Tennis The force that causes the Ball to change direction is the racquet impact.

Forces Can - Ball shape is compressed by the force of the club head on impact Cause a body to change shape Sporting example: Golf The force that causes the ball to change shape is the impact from the club head.

List what external factors act upon a golf ball in flight?

Newton’s Second Law of Motion When a force acts on an object, the motion experienced by the object is proportional to the size of the force and in the direction in which it is applied. Sporting Examples: “If you kick a football hard, it will go a long way” “If you kick a football softly it wont go very far” “If you hit a hockey ball to the left, it will go left” “If you hit a hockey ball to the right, it will go right”

Explain Newton’s 2 nd law in relation to Netball if the mass of the ball never changes.

Newton’s Third Law of Motion For every action there is an equal and opposite reaction. Sporting Examples: “If a rugby player pushes to the left with their foot, they swerve to the right. ” “A high jumper needs to push down on the ground to be able to go up. ” A football goalkeeper needs to push to the left with their feet in order to dive to the right. ”

N O TI E AC RC FO Reaction force is the goal keeper lifting into the air in the opposite direction N O TI E AC RC RE FO Action force is the goal keeper pushing down into the floor

Activities 1. What is Newton’s third law? Give three examples? 2. Which if Newton’s Law’s do you think is most important in performing freestyle. Justify you answer. 3. Give two examples of linear and curvilinear motion. Describe how they are different to justify your answer. 4. Complete the following problems: – A soccer player kicks a soccer ball weighing 0. 5 kg with an acceleration of 60 m/s/s. What is the force of the kick? – A high jumper applies force of 1000 N to the ground, which produces an acceleration of 15 m/s/s. What is the mass of the high jumper?

Centre of Mass An imaginary point which is movable and is where the mass of an object is concentrated. Centre Of Gravity

As the mass of the arms move up so will the centre of gravity Centre Of Gravity

Stability is dependant on the Centre of gravity being directly above the Base of Support Centre Of Gravity Base of Support

Stability Centre Of Gravity Stability is dependant on the Centre of gravity being directly above the Base of Support Line of Gravity Base of Support STABLE

Stability is dependant on the Centre of Gravity being directly above the Base of Support UNSTABLE Centre Of Gravity Line of Gravity Base of Support

Centre of Mass Remember Centre Of Gravity doesn’t always need to be inside the body

Stability is dependant on 4 things Position of the centre of gravity? Size of the base of support? Mass of the Athlete? Where the line of gravity is?

Types of Motion Linear – Occurs when an object moves in a straight line – Eg. running Curvilinear – When movement follows a curved path – Eg. Flight of the ball in golf

Types of motion Velocity – = DISPLACEMENT TIME Speed – = DISTANCE TIME Acceleration – The rate of change in velocity over time. NB: Distance is the length of the path travelled Displacement is the distance between the start and finish points. ‘as the crow flies’

Motion - Linear When a body moves in a straight line with all its parts moving the same DISTANCE, DIRECTION, and SPEED Everything is moving in the same direction at the same speed SPORTING EXAMPLE = THE BOB SLEIGH (TOBOGGAN)

Motion – curvilinear When a body or part of a body moves in a circle or part of a circle about a point (the axis of rotation). Circular motion about a point. i. e. The elbow being fixed when the forearm moves in a half circle in a tennis serve Axis of rotation SPORTING EXAMPLE = BENDING YOUR ARM IN A TENNIS SERVE

Motion – General = curvilinear +Linear General motion is a combination of Linear and Angular motion Sporting examples • Javelin • Wheel chair athletics • Swimming • Running

Bouyancy

Centre of Bouyancy

Activities 1. Explain how an athletes’ base of support and line of gravity affect their balance and stability 2. Discuss how a gymnasts centre of gravity may change during a routine. 3. Using your understanding of balance and stability justify the sloped design of the swimmer’s starting blocks (Hede, pg. 83) 4. What determines whether an object will float or not? 5. Why does a shot put sink when thrown in the pool when a rubber ball floats? 6. How is centre of gravity important in swimming? What other contributing forces are important and why? 7. Practical activities for COG and Centre of Bounancy will be complete in lifesaving lesson