Question

A uniform ladder of length 20.0m and weight 750 N is propped up against a smooth vertical wall with its lower end on a rough horizontal surface. The coefficient of friction between the ladder and this horizontal surface is 0.40.

(b) Work out and add the numerical values of each force clearly showing your justification in each case.

(c) Hence, calculate a value for the angle between the ladder and the wall if the ladder just remains in stable equilibrium.

Answer 1

So now sum vertical forces: You only have two (weightladder and floor upward).
Sum horizontal foces: wall force and friction at base.
Sum moments about any point: I recommend the floor contact point, you have ladder weight, and wall force then.

The angle should come put pretty quickly on the moment equation.

I will be happy to check your calcuations.

Answer 2

weight ladder plus floor upward: 750 + 20.0= 770N

wall force + friction at base: 20.0 + 0.40= 20.40N

I have no idea what you mean about sum moments about any point.

Answer 3

Wow, you have missed some class time.

Try this: http://info.ee.surrey.ac.uk/Teaching/Courses/ee1.el3/s07el3.pdf

Answer 4

That doesn't help me because I still don't understand it. Please can you at least direct me on how to go about the question as my work is due very soon.