Aluminum Ladder

PHYSICS HELP!! Coeffecient of static friction? A uniform 6.9 m tall aluminum ladder is leaning against a frictionless vertical wall. The ladder has a weight of 241 N. The ladder slips when it makes a 52 degree angle with the horizontal floor. Determine the coeffecient of static friction between the ladder and the floor we use the three conditions of equilibrium call Na the normal force of the ground up on the ladder and Nb the frictional force onthe ladder the frictionless vertical wall does not exert a vertical force onthe ladder, but it does exert a horizontal force, Fh vertical equilibrium gives us: Na = W where W is the weight of the ladder (eq.1) horizontal equilibrium gives us Fh=Nb but we also know that Nb= u Na = u W, so Fh = u W (eq. 2) the third condition is rotational equilibrium; where we sum torques around a point let's choose summing torques around the point where the base of the ladder touches the ground, that way we do not have to worry about torques due to Na and Nb (since they are zero due to a zero lever arm) the torques then are due to Fh and the weight; since the ladder is uniform, its weight acts as if it is concentrated at the center of mass torque due to Fh = Fh L sin 52 (where L is the length of the ladder) torque due to W = WL/2 cos52 these torques are equal and opposite, therefore Fh L sin 52= W/2 L cos 52 or Fh = W/(2 tan 52) = 241/(2 x 1.28)=94.1N we discovered above that Fh = u W, so we have that u=Fh/W = 94.1/241=0.39

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Ladder Construction – Safety In Design

Ladders are responsible for numerous deaths and injury each year, the majority are caused by improper use and faulty equipment. However, if used correctly and if they are in good condition, a ladder is the most useful, practical and convenient tool of working at height available.

One of the most important aspects is that you use the correct ladder for the job in hand; a step-ladder for ceiling work, an extension ladder for leaning against an outside wool or a roof ladder for working on roofs. But also its vital that the ladder is made of the correct material and is of of good quality.

Cheap and badly made ladders are dangerous and should never be used. In looking for a ladder here are some things to look out for:

Materials

Aluminium, is one of the most common materials for manufacturing ladders. Its light, strong and easily manipulated for manufacture. Aluminium ladders also don;t chip or crack when subjected to impact. Aluminium also doesn’t need to be painted and doesn’t suffer from severe corrosion.

Aluminum ladder

However, there are drawbacks to aluminium ladders. Aluminium does dent and a buckled ladder should not be used as it could be uneven. Aluminium is also a conductor of electricity and heat so should be avoided when bare electrics or extreme heat are present.

Fibre Glass is a very similar material to aluminium. Its not an alloy and is not susceptible to the elements and is very strong and even lighter than aluminium. Its far more brittle though, and can crack if impacted but it doesn’t conduct electricity so is often used around electricity.

Wood is a traditional material and still useful for ladders. Timber ladders are often made of combined hard and soft wood for strength and rigidity. However, they can crack and chip and need to be painted or varnished to avoid the elements.

Quality

When buying a ladder the quality should be checked carefully. Ensure any aluminium ladder is not bent or buckled and that a wooden or fibre glass ladder has no cracks, dents or chips. All rungs should be secure and if you are unsure – walk away!

About the Author

Richard N Williams is interested in ladders, extension ladders and step ladders. Please visit us website if you are interested in aluminium ladders or other types of ladders.