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 Kinematics and Dynamics Kinematics and Dynamics Physics Help Forum Apr 1st 2009, 05:32 PM #1 Junior Member   Join Date: Feb 2009 Posts: 3 Motion in a central force Hello, I have a problem with 2 questions of an exercie about an circular motion in a central force, which can help me are welcome; We 're interested in an artificial satellite, mass $\displaystyle m$, in circular orbit of radius $\displaystyle R$ around the Earth mass $\displaystyle M_E$ and radius $\displaystyle R_E$. I have already shown that the motion of the satellite was uniform by the Newton's laws of motion. Now I'd like some help to answer the following question : Show that the mechanical energy "E" of the satellite is related to its kinetic energy $\displaystyle E_k$ by E =- $\displaystyle E_k$.   Apr 1st 2009, 07:56 PM #2 Physics Team   Join Date: Feb 2009 Location: India Posts: 365 You know that the orbital velocity of a satellite is given by - V = sqrt(GM/r), where M is the mass of the earth and r is the distance of the satellite from the centre of the earth. If mass of the satellite be m then its kinetic energy K = (1/2)mV^2 = (1/2)GMm/r ..........(1) Next, its potential energy is given by U = - GMm/r ..............................(2) Mechanical energy (E) is the sum of the two- E = K + U = - (1/2)GMm/r ..............(3) From eq (1) and (3) it is clear that E= -K  Tags central, force, motion Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Dynamo Advanced Mechanics 2 Apr 20th 2009 11:31 AM sjhendrix06 Advanced Mechanics 2 Apr 2nd 2009 02:52 PM terry2 Kinematics and Dynamics 2 Jan 8th 2009 02:16 AM terry2 Kinematics and Dynamics 0 Nov 5th 2008 09:39 PM taureau20 Kinematics and Dynamics 0 Sep 27th 2008 02:52 AM