Physics and Loop Design

CENTRIPETAL FORCE
The average person on the street has heard of centrifugal force. When asked, they would describe this force as the one pushing an object to the outside of a circle. There is only one problem with this description. There is NO FORCE pushing an object to the outside.

For a person riding in a car while traveling in a circle, he perceives a force pushing him to the outside of the circle. But what force is physically pushing him? It can not be friction. Frictional forces oppose the direction of motion. It cannot be a normal force¹ . There is not a surface pushing the rider to the outside. To travel in a circle, a force pointing to the inside of the circle, or curve, is needed. The force pointing to the inside is called the centripetal force.

To understand a source for the misconception of the direction of this force, consider what it feels like when traveling around a corner in the back seat of a car. Everyone who has been in this situation knows that the passenger will slide to the outside of the curve. To understand that there is no force pushing the passenger to the outside, a change of reference frame is needed. Move the point of view from inside the car to a location outside, above, the car.

 OVERHEAD

OVERHEAD

OVERHEAD
CENTRIPETAL FORCE AND WHAT SUPPLIES IT

¹ The normal force is the force perpendicular to a surface. The floor is exerting a normal force straight up equal to your weight right now.