Sun 
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 × 10^{6} km (8.65 × 10^{5} 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 (10,000°F); 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. 
Energy 
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. 
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. 
Mass 
The quantitative or numerical measure of a body's
inertia, that is, of its resistance to being accelerated. 
Inertia 
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. 
Work 
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. 

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. 

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

Acceleration 
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. 

Momentum 
In classical mechanics, momentum (SI unit kg m/s, or,
equivalently, N•s) 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 
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. 