Biomechanics and Sports
This domain tests mechanical principles applied to sport: force, Newton's laws, levers, centre of gravity, equilibrium, friction and projectile motion. Expect application, not just definitions.
Core concepts
- Newton's laws: a body stays at rest or in uniform motion unless a net force acts; force = mass × acceleration; every action has an equal and opposite reaction.
- Levers: first class (fulcrum between effort and load), second class (load between fulcrum and effort), third class (effort between fulcrum and load). Most human joint levers are third class, favouring speed and range over force.
- Centre of gravity is the point where weight acts; stability improves with a lower centre, wider base and vertical line of gravity inside the base.
- Projectile motion: horizontal and vertical components are independent; in still air, 45° gives maximum range for a given release speed, but sport constraints change the optimum.
- Friction and impulse: friction can be helpful or harmful; impulse = force × time, so follow-through increases momentum change.
Worked example
In a biceps curl, the elbow is the fulcrum, the biceps supplies effort and the forearm plus weight is the load. Effort lies between fulcrum and load, so this is a third-class lever. Reasoning: the muscle must produce more force than the load, but the arrangement increases speed and range of the hand.
Traps
- Confusing mass with weight.
- Reversing lever classes.
- Assuming 45° is always the best release angle in games.
- Ignoring that action and reaction act on different bodies.