Biomechanics and Sports
This domain applies mechanics to movement: Newton's laws, types of motion, levers in the body and the factors that decide how far a projectile travels.
Newton's laws in sport
- First law (inertia): a body stays at rest or in uniform motion unless a force acts - a stationary ball needs the bat.
- Second law (F = ma): the same force accelerates a lighter object more.
- Third law: every action has an equal and opposite reaction - you push back on the ground to sprint forward.
Levers
First class: fulcrum between effort and load (nodding the head, a see-saw). Second class: load between fulcrum and effort (standing calf raise, wheelbarrow) - mechanically advantageous. Third class: effort between fulcrum and load (biceps curl) - the most common in the body, favouring speed and range at the cost of force.
Projectiles
Range depends on release speed, release angle, release height and gravity, with air resistance and spin modifying flight. In a vacuum the optimum is 45°; when release is above landing height, as in shot put, the optimum falls to roughly 40–42°.
Worked example
In a biceps curl the elbow joint is the fulcrum, the biceps insertion near the elbow is the effort, and the dumbbell in the hand is the load. Effort lies between fulcrum and load, so it is a third-class lever with mechanical advantage below 1: the muscle must produce more force than the weight, but the hand moves faster and through a larger range than the tendon. That is why the body uses this arrangement so often.
Traps that cost marks
- Placing the load between fulcrum and effort in a biceps curl.
- Quoting 45° for every projectile regardless of release height.
- Confusing angular motion about an axis with linear motion.