Cobra

Cobra (/ˈkōbrə/  pronunciation ) is the Portuguese word for "snake". In English and in some other languages, it has been adopted as the name for any of various species of venomous snakes. Most of those species are in the family Elapidae, all of which are venomous. Most of them can spread their neck ribs to form a flattened, widened hood.

Not all snakes commonly referred to as cobras are of the same genus, or even in the family Elapidae. The name "cobra" is short for cobra de capelo or cobra-de-capelo, which is Portuguese for "snake with hood", or "hood-snake". In some modern languages, such as Afrikaans, the other part of the Portuguese name was adopted, and the predominant name for a cobra in Afrikaans is kapel. When disturbed, most of these snakes rear up and spread their necks (or hoods) in a characteristic threat display, making them a favorite of snake charmers because of the dramatic effect. Long ago, snake charming was a religious ritual, though now it has become entertainment. Cobras, which may live up to 20 years, are found from southern Africa, through southern Asia, to some of the islands of Southeast Asia.

Force

In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described by intuitive concepts such as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.

The original form of Newton's second law states that the net force acting upon an object is equal to the rate at which its momentum changes with time. If the mass of the object is constant, this law implies that the acceleration of an object is directly proportional to the net force acting on the object, is in the direction of the net force, and is inversely proportional to the mass of the object

Related concepts to force include: thrust, which increases the velocity of an object; drag, which decreases the velocity of an object; and torque, which produces changes in rotational speed of an object. In an extended body, each part usually applies forces on the adjacent parts; the distribution of such forces through the body is the so-called mechanical stress. Pressure is a simple type of stress. Stress usually causes deformation of solid materials, or flow in fluids.