The figure below shows a planet traveling in a counterclockwise direction on an elliptical path around a star located at one focus of the ellipse. When the planet is at point A,
A)its speed is constant.
B)its speed is increasing.
C)its speed is decreasing.
D)its speed is a maximum.
E)its speed is a minimum.

Question

The figure below shows a planet traveling in a counterclockwise direction on an elliptical path around a star located at one focus of the ellipse. When the planet is at point A, 
A)its speed is constant. 
B)its speed is increasing. 
C)its speed is decreasing. 
D)its speed is a maximum. 
E)its speed is a minimum.

Quizplus · Accepted Answer

When the planet is at point A, it is at its closest point to the star (perihelion). According to Kepler's second law, the planet sweeps out equal areas in equal times, which means that it moves faster when it is closer to the star. As the planet approaches perihelion, its speed increases, and as it moves away from perihelion, its speed decreases. Therefore, since point A is the closest point to the star, the planet's speed is at its maximum, and it is decreasing.

The Figure Below Shows a Planet Traveling in a Counterclockwise