Gravity

Gravity

Gravity is one of the four basic forces. It is what keeps us from floating away and keeps the Moon in orbit around the Earth, and the planets in orbit around the Sun. Isaac Newton said, "Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion."

About Gravity

The gravity of Earth, denoted g, refers to the acceleration that the Earth imparts to objects on or near its surface. In SI units this acceleration is measured in metres per second per second (in symbols, m/s or ms) or equivalently in newtons per kilogram (N/kg or Nkg). It has an approximate value of 9.81m/s, which means that, ignoring the effects of air resistance, the speed of an object falling freely near the Earth's surface will increase by about 9.81metres (about 32.2ft) per second every second. This quantity is sometimes referred to informally as little g (in contrast, the gravitational constant G is referred to as big G). There is a direct relationship between gravitational acceleration and the downwards weight force experienced by objects on Earth, given by the equation F = ma (force = mass acceleration). However, other factors such as the rotation of the Earth also contribute to the net acceleration.