Ch 8Biomechanics and Sports — Class 12 Physical Education, concept-first.

Every sprint start, every curving free kick and every lift in the gym is governed by the laws of physics acting on the human body.

Biomechanics is the science of the movement of a living body — the way muscles, bones, tendons and ligaments work together to produce motion.

Sir Isaac Newton (1642–1727) was one of the greatest scientists and mathematicians in history. He set out three general rules describing how objects move, known today as Newton's Three Laws of Motion.…

Newton's First Law of Motion, also called the Law of Inertia, states that a body continues in its state of rest, or of uniform motion in a straight line, unless an external (resultant) force acts on i…

Newton's Second Law of Motion (the Law of Momentum) states that the rate of change of momentum of a body is proportional to the resultant force applied, and that this change takes place in the directi…

Newton's Third Law of Motion states that for every action there is an equal and opposite reaction: whenever one object (A) exerts a force on a second object (B), object B exerts a force of exactly the…

A lever is a type of simple machine, and the human body uses levers as its mechanism for movement. Although levers belong to the skeletal system, it is the muscles that supply the force to work them:…

There are three classes of lever, distinguished by which component — fulcrum, effort or load — lies in the middle.

The human leverage system is built for speed and range of movement rather than for force. Most muscles attach very close to the joint, giving short force arms and long resistance arms — the biceps for…

When we say that something is stable or balanced, we usually mean that it is not easily upset — it takes real effort to topple it. An unstable object, by contrast, is tipped over easily.

With respect to the state of a body, equilibrium is divided into two categories: static equilibrium and dynamic equilibrium.

Several factors decide how much equilibrium — how much stability — a body has. An athlete who understands them can set up a far more stable position.

The centre of gravity (CG) is the point at which the whole weight — or mass — of a body may be taken to be concentrated.

Friction is a force that opposes the motion between two surfaces that are in contact. It always acts in the direction opposite to the way an object is moving — or trying to move.

Friction is grouped into two broad kinds — static friction and kinetic friction — and kinetic friction is itself of three types.

Although friction is essential in sport, there are many situations where it must be reduced to save energy, cut wear, or let equipment and the body move more efficiently.

Friction is a classic example of a "necessary evil": sport could not happen without it, yet too much of it causes real problems.

A projectile is an object that, once thrown or dropped, keeps moving by its own inertia and is acted upon by only one real force — the downward pull of gravity (with air resistance also at work in pra…

The path a projectile follows — its trajectory or flight path — depends on six main factors: (a) gravity, (b) air resistance, (c) speed of release, (d) angle of release, (e) height of release, and (f)…

Projectile motion turns up throughout daily life, technology and especially sport. Because most sports involve the flight of a projectile — usually a ball — physics can be used to work out the optimal…

- Biomechanics is the science of the movement of a living body — how muscles, bones, tendons and ligaments work together — and it is part of kinesiology.