A planet moves in an elliptical orbit around the Sun. If T, V, E and L denote its kinetic energy, gravitational potential energy, total energy and angular-momentum magnitude, respectively, which is correct?
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Question

A planet moves in an elliptical orbit around the Sun. If T, V, E and L denote its kinetic energy, gravitational potential energy, total energy and angular-momentum magnitude, respectively, which is correct?

Options

G1 Physics · Accepted Answer

Step 1: A bound elliptical orbit has total energy E=−GMm/(2a)<0, where a is its semimajor axis. Step 2: T and V vary along the orbit; V is negative. Angular momentum is a fixed vector for planar central-force motion. Final answer: C — E is always negative.