## Why is the outward force in a loop-the-loop a “fictitious” force? Why isn’t it…

#### Why is the outward force in a loop-the-loop a “fictitious” force? Why isn’t it a “real” force?

A real force causes acceleration. If the outward “fictitious” force on a circling object were “real,” that object wouldn’t circle. It would accelerate outward. When you swing an object around on a string, you feel the object pulling outward on the string. But it isn’t itself being pulled outward by anything. What you’re feeling is the object’s inertia trying to make it travel straight. The inward force you’re exerting on it isn’t opposing some real force, it’s causing the object to accelerate inward.

## Can you explain the term centripetal?

#### Can you explain the term centripetal?

Centripetal means “directed toward a center.” A centripetal force is a force that’s directed toward a center. For example, a ball swinging around in a circle at the end of a string is experiencing a force toward the center of the circle—a centripetal force. Because the ball accelerates in the direction of the force, it accelerates centripetally. And because it experiences a fictitious force in the direction opposite its acceleration, it experiences an outward fictitious force away from the center of the circle. That fictitious force is called centrifugal “force.” However, you should always recognize that this outward “force” is not a force at all, but an effect caused by the ball’s inertia—its tendency to travel in a straight line.

## If all the kids on the merry-go-round are clustered around its center while it i…

#### If all the kids on the merry-go-round are clustered around its center while it is spinning at a constant angular velocity, then if all the kids were to “cautiously” move away from its pivot to the outer edges (while still spinning), would that cause the merry-go-round to slow down faster than if they had remained in the center?

Yes. When the kids move away from the center, the merry-go-round will slow down. If they then return to the center, the merry-go-round will speed up!