According to Newton's first law of motion, an object in motion will stay in motion unless there is an equal and opposite force acting against it (Psu.edu , 2016). This keeps the roller coaster train moving. When the roller coaster train enters the loop loop, the centripetal force (Fc) begins to act on the rider in order to keep the roller coaster train moving throughout the loop loop. It is the total force of inertia, the upward force known as the "apparent" weight (Fs) exerted by the roller coaster train, the downward pull of gravity (Fg) and the centripetal acceleration (Ac) which act on the roller coaster train during its movement. through the vertical circle, refer to the figure