When a roller coaster goes in an upside-down loop, the force responsible for circular motion is acting toward the top of the loop. This force is known as the centripetal force, which is directed towards the center of the circular path. In the case of an upside-down loop, the centripetal force acts inwards towards the top of the loop to keep the roller coaster moving in a curved path without flying off.
To better understand this concept, imagine a ball attached to a string and spun around in a circle. The tension in the string provides the centripetal force that keeps the ball moving in a circular path. Similarly, in the case of the roller coaster in an upside-down loop, the force acting towards the top of the loop is essential to prevent the roller coaster from falling down due to gravity.
Therefore, when a roller coaster goes through an upside-down loop, the force responsible for circular motion is acting toward the top of the loop to maintain the coaster's trajectory and ensure the safety of the riders.
