Question

Quick Quiz 13.4 A comet moves in an elliptical orbit around the Sun. Which
point in its orbit (perihelion or aphelion) represents the highest value of
(a) the speed of the comet, (b) the potential energy of the comet-Sun system,
(c) the kinetic energy of the comet, and (d) the total energy of the comet-
Sun system?​

Answer 1

Answer:

Answer

A comet while going on elliptical orbit around the Sun has constant angular momentum due to no external torque and total energy due to Law of conservation of energy at all locations but other quantities vary with locations.

(a)

Since angular momentum is constant, L=

r

mv

2

is constant. As r changes in elliptical orbit, speed is not constant.

(b)

Since angular momentum is constant, L=mω

2

r is constant. As r changes in elliptical orbit, angular speed is not constant.

(c)

Angular momentum is constant because there is no external torque.

(d)

Since speed is not constant, Kinetic Energy is not constant.

(e)

Total energy is constant by law of conservation of energy.

T.E.=P.E.+K.E.=constant

Since K.E. is not constant, P.E. is not constant.

(f) Total energy is constant by law of conservation of energy.