A point mass m is suspended from a light thread of length ℓ and whirled in a horizontal circle at constant speed. In the frame moving with the mass, which force diagram is correct?

Question

G1 Physics · Accepted Answer

In the frame stationary with the mass, the mass is at rest but the frame is non-inertial. The real forces are tension and weight, and a centrifugal pseudo-force must also be included. The diagram containing T, W and outward pseudo-force F is Image 3. Hence C.