Select two answers

Question

An amusement park ride called "The Giant Swings" consists of seats suspended by chains from a platform. After the passengers are secured in their seats, the platform rotates and the passengers swing outward and they move around in a horizontal circle at a constant speed. While the ride is in operation, which of the following statements are correct?

A. There is a net force away from the center of the ride that causes the passengers to swing outward while moving around the circular path.

B. The tensionin the chain is greater than the weight of the passenger/swing.

C. The velocity of the passengers is constantly changing as they go around the circle.

D. The passengers are acceleration in the direction of the tension force.

Answer 1

Using an inertial frame of reference, there are two forces acting on the person/chair: the force of gravity W pointing down, and the tension in the chain T pointing at an angle (say "northwest"-ish if you look at a chair to the right of the axis of rotation).

A. Is wrong because there is no outward force in this frame of reference (there would be a force in that direction, the centrifugal force, in the non-inertial frame of reference rotating with the person, but even that force would not be a net force).

B. Is correct because T cosθ = W (Newton's second law in the vertical direction). From here, T = W/cosθ, which leads to T > W because cosθ < 1. I defined θ as the angle between the chain and the vertical.

C. Is correct because the velocity is continuously changing even though its magnitude (the speed) is not.

D. Is wrong because the acceleration of the passengers is the centripetal acceleration and is due to the horizontal component of T (T sinθ).