Speed, Velocity and Acceleration

When a car accelerates at a constant rate (a),
its velocity (v) increases steadily,
while the total distance travelled (x) increases exponentially.

The concepts of speed, velocity and acceleration are vital to describing the motion of all bodies in mechanics. Speed and velocity are commonly treated as if they are interchangeable, but strictly speaking, speed is a measure of a body's rate of motion in any direction, while velocity is a measure of a body's rate of motion in any direction, while velocity is a measure of motion in a specific direction. Both can be measured in the same units (such as metres per second), but speed is a directionless or 'scalar' quantity, while velocity is a directed or 'vector' quintity. In most situations, it's far more useful to know an object's velocity than its speed.

Darwin

Hello dear friend,
Everyone and all students in the world knows Darwin.

Darwin, in simple words says that every kind of the living creatures in the earth, has Evolution in the centuries. Specifically, as random genetic mutations occur within an organism's genetic code, the beneficial mutations are preserved because they aid survival - a process known as "natural selection".

What is the matter?

What is the matter, molecules, atoms, electrons and protons?

Today, the scientific community had published hundred of theories about the phenomena of matter.

For example the rain: Rain is a type of precipitation, a product of the condensation of atmospheric water vapour that is deposited on the earth's surface (answers.com). It is not something difficult to understand scientifically.


And of course, all of us, had seen rain many times in our life. So, the rain is something happening in the collected water at sky.