A uniform beam long and of negligible mass is hinged to a wall at point
PHYSICS · Multi-part · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
A uniform beam 2.40m long and of negligible mass is hinged to a wall at point A. The beam is held in a horizontal position by two vertical chains attached to its upper surface: Chain 1 is connected 0.60m from the hinge and supports a hanging 240N sign; Chain 2 is connected at the free end of the beam but its tension T is unknown.
Assume the sign’s entire weight acts at the attachment point of Chain 1. Ignore the weights of the beam and chains.
(a) Draw a labeled force diagram for the beam, showing all forces that exert torques about point A and indicating their lines of action.
(b) Explain which of the identified forces produce clockwise torques about point A and which produce counter-clockwise torques.
(c) The beam remains perfectly horizontal and does not rotate. Using this information, determine the numerical value of the unknown tension T in Chain 2.
(d) The hinge at A is replaced by a friction-free pin that cannot exert any vertical force component. Predict qualitatively how your answer to part (c) would change, if at all, and justify your prediction.