Question

If Pluto orbits the Sun in an elliptical orbit. Choose the correct option which is true of Pluto’s orbit?
(A) The gravitational force acting between Pluto and the Sun must point in the direction of Pluto’s velocity.
(B) The gravitational force between Pluto and the sun is greater when Pluto is farthest from the sun
(C) The speed of the Pluto is greatest when Pluto is closest to the sun
(D) The gravitational force between the sun and Pluto is constant at all points in Pluto’s orbit

Answer 1

Use the concept of energy conservation because the kinetic and potential energy of Pluto varies according to its position in the elliptical orbit. The total energy is conserved, so if Pluto's potential increases, then Pluto's kinetic energy will decrease and vise versa.

Complete step by step answer:
We know that all the planets revolve around the Sun; the Sun's revolution occurs because the Sun also has a gravitational effect like earth. The Sun tends to attract the planets towards it, but the Sun's effect is different from the earth. The Sun is at the center of our solar system, and eight planets revolve around the Sun in a circular or elliptical orbit. Our earth is the third planet from the Sun and the only planet in the solar system with plants, animals, and humans.

The potential of Pluto relates directly to the distance at which it is revolving. If the distance between the Sun and Pluto is more, it means that potential energy is more. But we knew that the total energy is conserved, so Pluto's kinetic energy will decrease due to an increase in potential energy. When Pluto comes closer to the Sun, its potential energy will decrease, and its kinetic energy will increase. So, due to an increase in kinetic energy, Pluto revolves in orbit with fast speed.

Therefore, if Pluto orbits the Sun in an elliptical orbit, Pluto's speed is greatest when Pluto is closest to the Sun.

So, the correct answer is “Option C”.

Note:
The planets' positions are different from the Sun and revolve around the Sun at a different speed. The planets revolve with the different speeds in orbit because of various factors like the mass of the planet, gravitational effect, and many others. Due to the speed variation, the kinetic energy of the planes varies.