Question

A planet travels in an elliptical path around a star, as shown in the figure. As the planet gets closer to the star, the gravitational force that the star exerts on the planet increases. Which statement of reasoning best supports and correctly identifies what happens to the magnitude of the force that the planet exerts on the star as the planet gets closer to the star?

The force remains constant because the mass of the planet remains constant.
A

The force increases because it is part of a Newton’s third law pair of forces with the force that the star exerts on the planet.
B

The force decreases because the planet increases its speed as it gets closer to the star.
C

The force fluctuates such that it increases and decreases because the planet does not travel in a perfectly circular path.

Answer 1

B. The force increases because it is part of Newton’s third law pair of forces with the force that the star exerts on the planet.

Step-by-step explanation:

According to the universal law of gravitation, the force between the two objects is,

`F = G (Mm)/(x^(2) )`

From the equation, it is clear that when the magnitude of the distance between the two bodies decreases, the magnitude of the force increases.

According to newton's third law of motion, the force acting on the body is always equal to its recreational force in the opposite direction.

Hence, the force increases because it is part of Newton’s third law pair of forces with the force that the star exerts on the planet.