Biomechanics - Biomechanical principles - A-Level Physical Education

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Biomechanics - Biomechanical principles

infoWhy this? The Newton’s Laws, Forces and Use of Technology unit is introduced in Year 12 as students’ first experience of biomechanics at A Level. While much of the content is new, it provides the essential foundation for understanding how scientific principles can be applied to movement and performance in sport. Students develop knowledge of force, motion and technological analysis, enabling them to explain and evaluate sporting performance using biomechanical concepts.

scheduleWhy now? This unit lays the groundwork for more advanced biomechanical principles studied in Year 13, where students will build upon their understanding to analyse movement in greater depth and apply complex theoretical concepts to sporting situations. Studying this unit now ensures students have the core knowledge and terminology required for success in later biomechanics topics.

Newton’s first law states that a body remains at rest or moves with constant velocity unless acted on by a net force; inertia is the tendency to resist a change in motion.
Newton’s second law states that a net force causes acceleration in the direction of the force, expressed as `F = ma`.
Newton’s third law states that when one body exerts a force on another, the second body exerts an equal-sized, opposite-direction force on the first body.
Velocity is speed in a stated direction, while acceleration is the rate at which velocity changes, calculated using `a = (v - u)/t`.
Momentum is the product of mass and velocity, calculated using `p = mv`, so a faster or more massive performer has greater momentum.
Weight is the force caused by gravity acting on a mass and is calculated using `W = mg`, where gravitational field strength on Earth is approximately `9.8 N/kg`.
Balanced forces produce zero net force and no acceleration, whereas unbalanced forces produce a net force and cause acceleration, deceleration or a change of direction.
Vertical forces in sport commonly include weight and ground reaction force, while horizontal forces commonly include friction, air resistance and applied forces.
Friction is a contact force that opposes relative motion, and its size is affected by the normal contact force and the nature and condition of the surfaces.
Air resistance acts opposite to motion and increases with speed, frontal area, less streamlined shape and greater air density.
The centre of mass is the point at which the mass of a body can be considered to be concentrated and through which its weight acts.
The position of the centre of mass changes with body shape, posture, limb position, mass distribution and the position of external loads or equipment.
Stability generally increases when the centre of mass is lower, the base of support is wider and the line of gravity remains well inside the base of support.
A free body diagram represents an object as a point or simple shape and uses labelled arrows to show the direction and relative size of every external force acting at one instant.
A lever system consists of a rigid lever rotating around a fulcrum, with an effort force acting to move a load or resistance.
In a first-class lever, the fulcrum lies between the effort and load, as when the triceps extend the elbow.
In a second-class lever, the load lies between the fulcrum and effort, producing a mechanical advantage because the effort arm is longer than the load arm, as when standing on tiptoes.
In a third-class lever, the effort lies between the fulcrum and load, producing a mechanical disadvantage but allowing a greater range and speed of movement, as during a biceps curl.
Limb kinematics uses video or motion-capture data to measure movement variables such as displacement, joint angle, velocity and acceleration, while force plates measure the size, direction and timing of ground reaction forces.
Wind tunnels allow aerodynamic drag and streamlining to be tested under controlled conditions; reliable measurements are repeatable, while valid measurements accurately assess the intended variable.

rocket_launchYou must be able to

Apply Newton’s three laws to explain sporting actions, identifying inertia, the net force and the action–reaction force pair.
Calculate force, acceleration, momentum and weight using `F = ma`, `a = (v - u)/t`, `p = mv` and `W = mg`, including correct units.
Draw free body diagrams with labelled force arrows beginning at the body or centre of mass and showing their direction and relative magnitude.
Determine whether forces are balanced or unbalanced by resolving horizontal and vertical forces and linking the net force to the body’s resulting acceleration.
Analyse how performers and equipment manipulate friction and air resistance to improve grip, speed, control or safety.
Assess a performer’s stability by locating the centre of mass, base of support and line of gravity and explaining how changes in posture affect stability.
Draw and classify first-, second- and third-class lever systems by correctly locating the fulcrum, effort and load.
Evaluate a lever’s mechanical advantage by comparing the effort-arm and load-arm lengths and linking their ratio to force, speed and range of movement.
Interpret information from limb kinematics, force plates and wind-tunnel testing, and judge whether the measurements are reliable and valid.

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