Basic Science Knowledge

  Keplers’s Laws of Planetary Motion: 1 st law ( Law of Orbits ): Every planet moves around the sun in elliptical orbit with the sun at one of the foci of the elliptical orbit. 2 nd   law ( Law of Areas): The line joining the planet to the sun sweeps over equal areas in equal intervals of time.                                                             Area of SAB = Area of SCD  2 nd   law tells us that a planet does not move with constant speed around the sun. It speeds up while approaching the nearest point called ‘ perigee’ and slows downs while approaching the farthest point called ‘ apogee’. therefore, distance covered on the orbit with in the given interval of time at perigee is greater than that at apogee such that areas swept are equal. 3 rd Law ( Law of periods): The square of the time periods of revolution of...

  Gravitational Forces of the earth or Gravity A force is necessary to produce motion in a body. A body dropped from a height falls toward the earth. It indicates that the earth exerts a force of attraction (called gravity) on the body. In fact, the earth attracts all the object its centre. The force with which the earth pulls the object toward it is called the gravitational force of the earth or gravity. The gravitational force between the sun and the earth keeps the earth in uniform circular motion around the sun. The gravitational force of the earth (or gravity) is responsible - l  For holding the atmosphere above the earth. l  For the rain falling to the earth. l  For flow of water in the rivers. l  For keeping us firmly on the earth. l  For the revolution of moon around the earth, etc. The gravitational force between the earth and the moon causes tides in the sea. Think why tides are high during full moon and new moon day. A few facts about Lunar Tides...