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 a fictitious 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 of the real forces acting on them.

Short answer

The unreal force acting opposite to gravity, which pins the riders to the wall. A real force acts when the floor is dropped and a downward force due to gravity is observed.

Step-by-step solution

Definition of Fictitious force

When a body’s motion describes non inertial frame of reference a force appear to be working on it is called Fictitious Force.

Explaining inertial frame of reference

The fictitious force pins the riders to the gravitational force. This is a force which acts in the opposite direction of gravity. Now the floor drops away, so a force acts in the downward direction, and an inertial force acts in the upwards direction due to Newton’s third Law.

In the vertical direction, the riders are subject to a downward force of mg due to gravity, and upward force of$\mu N$due to friction. N is the cumulative normal reaction between the riders and the wall, while m is the cumulative mass of the riders.

So, we can conclude. it is the unreal force acting opposite to gravity, which pins the riders to the wall. A real force acts when the floor is dropped and a downward force due to gravity is observed.