Explain how inertia and the shape of a loop counteract the force of gravity to keep riders from falling out when a roller coaster goes through a loop traveling upside down

When a roller coaster car goes through a loop, inertia keeps it from being pulled down by gravity. Inertia is the tendency of an object to resist a change in its motion, meaning that an object (the roller coaster car) which is already moving will resist forces that try to stop it. It will continue to try to move in a constant speed in a constant direction, even if other forces are slowing it down. The shape of the loop in a roller coaster is made so that the car can travel up it without losing its momentum. This is why a roller coaster car needs to be travelling at high speeds to go through a loop. If it weren't travelling quickly enough, the forces of gravity would pull it down before it could make it all the way through the loop.