Physics ----



The star around which the Earth revolves, and the planet's source of light and heat, hence life. The Sun is a globe of gas, 1.4 106 km (8.65 105 mi) in diameter with a mass 333,000 times the Earth, held together by its own gravity. The surface temperature of the Sun is about 6000 K (10,000F); since solids and liquids do not exist at these temperatures, the Sun is entirely gaseous. Almost all the gas is in atomic form, although a few molecules exist in the coolest surface regions, such as sunspots.


The capacity of a physical system to do work.

Solar energy

Energy from the sun. Solar Energy supports life on Earth and drives the Earth's weather.  Solar energy predominantly arrives in the form of infrared, visible and ultraviolet light, and is either returned back to space or is absorbed.  Nearly all of the absorbed energy is converted directly to heat.


1. A form of energy associated with the motion of atoms or molecules and capable of being transmitted through solid and fluid media by conduction, through fluid media by convection, and through empty space by radiation.

2. The transfer of energy from one body to another as a result of a difference in temperature or a change in phase.


The quantitative or numerical measure of a body's inertia, that is, of its resistance to being accelerated.


That property of matter which manifests itself as a resistance to any change in the motion of a body. Thus when no external force is acting, a body at rest remains at rest and a body in motion continues moving in a straight line with a uniform speed (Newton's first law of motion). The mass of a body is a measure of its inertia.


Mechanical Work is the amount of energy transferred by a force when a force is applied to a body that is moving in such a way that the force has a component in the direction of the body's motion. Thus work is done on a weight that is being lifted, or on a spring that is being stretched or compressed, or on a gas that is undergoing compression in a cylinder.

When the force acting on a moving body is constant in magnitude and direction, the amount of work done is defined as the product of just two factors: the component of the force in the direction of motion, and the distance moved by the point of application of the force.



That influence on a body which causes it to accelerate. In this way, force is defined through Newton's second law of motion.  This law states in part that the acceleration of a body is proportional to the resultant force exerted on the body and is inversely proportional to the mass of the body.  Newton's second law inextricably links mass and force. See also Acceleration; Mass.



A vector quantity whose magnitude is a body's speed and whose direction is the body's direction of motion.



The time rate of change of velocity. Since velocity is a directed or vector quantity involving both magnitude and direction, a velocity may change by a change of magnitude (speed) or by a change of direction or both.


Distance Moved

An extent, measured or unmeasured, of linear space: length, space, stretch.



In classical mechanics, momentum (SI unit kg m/s, or, equivalently, Ns) is the product of the mass and velocity of an object.  The amount of momentum that an object has depends on two physical quantities: the mass and the velocity of the moving object in the frame of reference.


Kinetic Energy

The energy possessed by a body because of its motion, equal to one half the mass of the body times the square of its speed.


Pressure is the ratio of force to the surface area over which it is exerted. Though solids exert pressure, the most interesting examples of pressure involve fluids that is, gases and liquids and in particular water and air.