Gravitational Fields

• The gravitational field strength at the surface of Earth is approximately 9.8 N/kg.
• Gravity is an attractive force between two masses, with the magnitude of the force being proportional to their product and inversely proportional to the square of the distance separating them.
• Gravitational field is a region of space where a mass experiences a force due to the gravitational attraction of another mass
• Center of mass is the average position of the distribution of mass
• Newton's Law of Gravitation states that the gravitational force between two point masses is proportional to the product of their masses and inversely proportional to the square of their seperation
• Inverse square law - The observed intensity of a specified physical quantity is inversely proportional to the square of the distance from the source of that physical quantity
• Gravitational Field Strength is the gravitational force exerted per unit mass on a small object placed at that point
• Gravitational potential is the work done per unit mass bringing in a mass from infinity to the point
• Gravitational potential is always negative

  • Gravitational force is always attractive
  • potential at infinity is defined as zero
  • potential decreases when mass moves in direction(along) the field lines
• Gravitational Potential energy of a mass at a point in the gravitational field of another mass is the work done in bringing that mass from infinity to that point
• Gravitational potential energy difference between two points is the work done in moving a mass from one point to another
• Kepler's third law of planetary motion states that for planets or satellites describing circular orbits about the same central body, the square of the period is proportional to the cube of the radius of the orbit
• Geostationary Orbits -

  • equatorial orbit
  • Period is 24 hrs
  • From west to east
• Geostationary Satellite is a satellite which appears to be above a certain point on earth
• Escape velocity is the speed a satellite needs to escape the gravitational pull of a planet and get into orbit
• The formula for escape velocity is sqrt(2GM/r)