Question

In one amusement park ride, riders enter a large vertical barrel and stand against the wall on its horizontal floor. The barrel is spun up, and the floor drops away. Riders feel as if they are pinned to the wall by a force something like the gravitational force. This is an inertial force sensed and used by the riders to explain events in the rotating frame of reference of the barrel. Explain in an inertial frame of reference (Earth is nearly one) what pins the riders to the wall, and identify all forces acting on them.

a) Centripetal force; gravity and normal force
b) Inertia; friction and tension
c) Centrifugal force; gravitational force
d) Magnetic force; air resistance

Answer 1

Riders in the spinning barrel of an amusement park ride feel pinned to the wall by centripetal force, which is the real force acting on them in an inertial frame of reference, along with gravitational force.

Step-by-step explanation:

In the described amusement park ride, riders are pinned to the wall due to the centripetal force. When the barrel spins, the riders are in motion with it, and the wall of the barrel provides the centripetal force needed to keep them moving in a circular path. The force that riders feel, sometimes mistaken for a centrifugal force, is actually the result of their body's inertia trying to move in a straight line while the barrel's wall forces them to move in a circle.

The gravitational force continues to act on the riders, pulling them down, but the normal force is removed when the floor drops away. Thus, the riders feel pinned to the wall by the centripetal force provided by the wall, and the two forces acting on them in this inertial reference frame are centripetal force and gravitational force.