Question

A uniform beam of length L and mass m is inclined at an angle θ to the horizontal (see figure below). Its upper end is connected to a wall by a horizontal rope and its lower end rests on a rough horizontal surface.

(a) In the free body diagram for the beam, there are 4 forces are acting on it. Name these forces, giving numerical values where appropriate, and their directions (known or if unknown, your assumed directions). Also state where these forces are acting.

(b) What are the three conditions for static equilibrium?

(c) For the condition that involves torques, explain how you would apply it to this problem. State where your choice of axis of rotation are, which forces exert torques about this axis including their signs and numerical values where appropriate. Do not solve for anything.

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Answer 1

c) For the equation involving torque,

We need to take lower end as the pivot,

Reason:

While taking a torque equation , We need to consider to eliminate maximum number of unknown forces as possible,

The normal force and friction acting at the lower end are eliminated by taking lower end as pivot.

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