Editing Reaction (physics) (section)

===Interaction with ground===
When something is exerting force on the ground, the ground will push back with equal force in the opposite direction. In certain fields of applied physics, such as [[biomechanics]], this force by the ground is called '[[ground reaction force]]'; the force by the object on the ground is viewed as the 'action'.

When someone wants to jump, he or she exerts additional downward force on the ground ('action'). Simultaneously, the ground exerts upward force on the person ('reaction'). If this upward force is greater than the person's weight, this will result in upward acceleration. When these forces are perpendicular to the ground, they are also called a [[normal force]].

Likewise, the spinning wheels of a vehicle attempt to slide backward across the ground. If the ground is not too slippery, this results in a pair of [[friction]] forces: the 'action' by the wheel on the ground in backward direction, and the 'reaction' by the ground on the wheel in forward direction. This forward force propels the vehicle.