Final answer:
Riders in a rotating barrel at an amusement park feel pinned against the wall due to a centripetal force, which is the true force acting to keep them in circular motion against the tendency of inertia.
Step-by-step explanation:
The true or false statements in question revolve around principles of physics, specifically involving energy conversion, motion, and forces. When it comes to the amusement park ride where riders are pinned against the wall of a rotating barrel, the explanation from an inertial frame of reference is that the riders are experiencing a centrifugal force.
This centrifugal force is not a real force but is the result of inertia. In an inertial (non-accelerating) frame of reference, the real force pinning the riders against the wall is the centripetal force, which is an inward-directed force provided by the wall of the barrel. It is this centripetal force that keeps the riders in a circular path, as opposed to following a tangent to the circle which is the natural tendency due to inertia. The other real force acting on the riders is gravity, pulling them towards the ground.