According to Newton's first law of motion, a moving object will stay in motion unless there is an equal and opposite force acting against it (Psu.edu, 2016). Therefore, the roller coaster train remains in motion. As the roller coaster train enters the loop, centripetal force (Fc) begins to act on the rider to keep the roller coaster train traveling through the loop. It is the total inertia force, the upward force known as "apparent" weight (Fs) exerted by the roller coaster train, the downward force of gravity (Fg), and the centripetal acceleration (Ac) acting on the roller coaster train while traveling. through the vertical circle, refer to the Figure