Question

A moon orbits a planet in a circular orbit so that its velocity along the circular path changes continuously with time. Explain how the force of gravity changes the moon's velocity.

Answer 1

Answer: The Earth exerts a gravitational force on the Moon which acts as a centripetal force, directed toward the center of the Earth which creates a centripetal acceleration, of which is also directed toward the center of the Earth causing the velocity of the Moon to constantly change direction in a circular orbit.

Explanation:



The force that causes objects to follow a circular path is called the centripetal force and acts towards the center of the circle. Gravitational force on the other hand is the force that objects exerts on each other. As shown on the attached picture when an object moves in a uniform circular motion, its velocity is always in the direction of the tangent of the orbit. This accounts for the constant change in velocity of the object as it is moving around the circle. Furthermore the acceleration of the object which is the moon in this case is directed towards the center of the circle which accounts for the changing direction of the velocity of the moon. Simply the Earth's gravity pulls the Moon in an orbit with circular motion.