Astronomy Practice Exam

What is a characteristic of centripetal motion in space?

1. It requires no force

2. It is dependent on mass alone

3. It involves constantly changing velocity

4. It only occurs in a vacuum

The correct answer is: It involves constantly changing velocity

A key characteristic of centripetal motion is that it involves constantly changing velocity. This occurs because, in centripetal motion, an object moves in a circular path. Although the object's speed may remain constant, its direction is continuously changing, leading to a change in velocity. Velocity is a vector quantity that depends on both speed and direction, so even with a constant speed, the alteration in direction signifies a change in velocity. In the context of motion in space, it's essential to recognize that the gravitational force, or another centripetal force, is what keeps the object in a circular path. This continuous change in direction is what defines centripetal motion and distinguishes it from linear motion. Thus, the motion is characterized by a constant centripetal acceleration directed towards the center of the circular path, which is what maintains the object's circular trajectory. The other options do not accurately describe this fundamental aspect of centripetal motion. For instance, it's not true that no force is required, as centripetal force is essential for maintaining this motion. Additionally, centripetal motion does not depend solely on mass; rather, it also requires a balance of forces that depend on speed and the radius of the circular path. Lastly, while centripetal motion