Overhead view: A circular turntable of radius 0.40 m can rotate freely about its…
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Overhead view: A circular turntable of radius 0.40 m can rotate freely about its fixed central vertical axis.
Three identical forces of magnitude 15 N are applied simultaneously at the rim.
• Point P lies at the easternmost edge of the turntable. A force at P points due north (tangent to the rim).
• Point Q lies at the northernmost edge. A force at Q points straight toward the center of the turntable.
• Point R lies at the westernmost edge. A force at R is directed 45° below the local tangent, halfway between due south (tangent direction) and straight toward the center.
Assume “clockwise” and “counter-clockwise” are defined from an overhead perspective.
(a) For each point (P, Q, R) explain whether the entire 15 N contributes to producing rotation, none of it does, or only a portion does. Support each answer by discussing both the direction of the force and its line of action relative to the axis.
(b) Rank the magnitudes of the torques produced by the three forces from largest to smallest. Clearly indicate any ties and justify your ranking qualitatively—no numerical calculation is required.
(c) Indicate the rotational sense (clockwise or counter-clockwise) of the single largest torque identified in part (b), and explain your reasoning.