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 =- $\displaystyle E_k$.