# Physics A2 Level

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1. 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
2. Gravitational field strength
• force field: a region in which a body experiences a force
• Radial field: field lines are like spokes on a wheel, directed towards the centre
• Uniform field: field lines are parallel and equally spaced
• g=F/m
• In a radial field g=GM/r2
3. 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 zero
• work done in moving mass: W=mV
• V in a radial field: V=-GM/r
• gravitational field strength is the negative of the potential gradient: g=-V/r
4. 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
 Author: koolcookie11 ID: 123830 Card Set: Physics A2 Level Updated: 2011-12-22 12:28:19 Tags: physics alevel gravitational fields Folders: Description: Gravitational Fields Show Answers: