A uniform horizontal beam 1.20 m long is rigidly attached to a wall at its left end
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A uniform horizontal beam 1.20 m long is rigidly attached to a wall at its left end, point O. Three external forces act on the beam as described below.
• Force 1: 40 N directed upward, applied at point A located 0.30 m to the right of O and perpendicular to the beam.
• Force 2: 25 N directed toward the right along the length of the beam, applied at point B located 0.60 m to the right of O.
• Force 3: 35 N directed downward at an angle of 60° below the horizontal, applied at point C, the free right end of the beam.
Assume the beam’s own weight is negligible compared with the applied forces.
(a) For each of the three forces, state whether it produces zero or non-zero torque about point O and justify your answer in terms of the line of action of the force.
(b) For every force that produces a non-zero torque about O, indicate whether the torque tends to rotate the beam clockwise or counter-clockwise as viewed from the wall. Explain your reasoning.
(c) Without carrying out a numerical calculation, predict qualitatively the effect on the magnitude of the torque produced by Force 3 if its point of application were moved to a distance 1.50 m from O while its direction and magnitude remain unchanged. Justify your prediction.