# Physics A2 Level

 Newton's law of gravitation Assumes that the gravitational force between any two point objects is: always an attractive force, proportional to the mass of each object and proportional to 1/r2 (r is distance apart)gravity is a universal force acting between all mater Gravitational field strength force field: a region in which a body experiences a forceRadial field: field lines are like spokes on a wheel, directed towards the centreUniform field: field lines are parallel and equally spacedg=F/mIn a radial field g=GM/r2 Gravitational potential the gravitational potential at a point in a gravitational field is the gpe per unit mass of a small test mass. It is equal to the work done per unit mass to move a small object from infinity to that point as the gravitational potential at infinity is zerowork done in moving mass: W=mVV in a radial field: V=-GM/rgravitational field strength is the negative of the potential gradient: g=-V/r Orbits of planets and satellites v=square root (GM/r)T=square root(4pi2r3/GM)A satellite's total energy is constant, so kinetic and potential energy is also constant (KE + PE = TE)Geosynchronous orbit: always above the same point on Earth, same angular speed as the Earth Authorkoolcookie11 ID123830 Card SetPhysics A2 Level DescriptionGravitational Fields Updated2011-12-22T12:28:19Z Show Answers