Mechanics · Moments
Chapter 1 · 3
The idea
Ladders, pegs and hinged rods in equilibrium
How to keep a leaning ladder, a rod resting on a peg or rail, or a hinged rod in equilibrium: draw every contact force the right way, take moments about the point that removes the most unknowns, resolve twice, and use friction's limit to find the coefficient of friction, how far a person can climb, the largest push, or the magnitude and direction of the force at a hinge.
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Mechanics · Moments
Ladders, pegs and hinged rods in equilibrium
How to keep a leaning ladder, a rod resting on a peg or rail, or a hinged rod in equilibrium: draw every contact force the right way, take moments about the point that removes the most unknowns, resolve twice, and use friction's limit to find the coefficient of friction, how far a person can climb, the largest push, or the magnitude and direction of the force at a hinge.
Why it works
What holds a leaning ladder up
A painter leans a uniform ladder , m long and of weight N, against a smooth vertical wall. Its foot is on rough horizontal ground m from the wall, and its top is m up the wall. Will it stay put, and how high can she climb?Four forces act: the weight N at the midpoint (the ladder is uniform), the push of the smooth wall, straight out from it, and at the ground's upward push and its friction . Friction points towards the wall: is the only other horizontal force, so without the foot would skid out.Keep reading — free
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