BM - Forces

Force

A push or pull that can start, stop, speed up, slow down, or change the direction of movement.

Magnitude

The size or strength of a force.

Direction

The way a force is acting; important because force must be applied in the right direction to improve movement.

Internal forces

Forces that act inside the body, such as muscle force, tendon tension, ligament tension, joint compression, and bone stress.

External forces

Forces that act on the body from outside, such as gravity, ground reaction force, friction, contact, and equipment load.

Gravity

A non-contact force that pulls objects toward Earth.

Weight

The force of gravity acting on a mass; calculated as weight = mass × gravity.

Normal contact force

The force from a surface pushing back against the body, such as the ground pushing back into the foot.

Friction

A force that resists sliding between two surfaces and helps with grip, traction, running, lifting, and change of direction.

Static friction

Friction that acts before sliding starts; usually stronger and helps prevent slipping.

Dynamic friction

Friction that acts when surfaces are already sliding.

Resultant force

The overall force after all forces acting on an object are combined; balanced forces mean no acceleration, unbalanced forces cause movement change.