# Homework Help: Finding a friction force (ladder leaning against a wall )

1. Nov 6, 2009

### Linus Pauling

1.

Suppose that the actual coefficent of friction is one and a half times as large as the value of . That is, . Under these circumstances, what is the magnitude of the force of friction that the floor applies to the ladder?
Express your answer in terms of , , , , , and . Remember to pay attention to the relation of force and .

2. static friction = magnitude of force in x direction, opposite sign

3. Ok, I had two exams today and I just almost went crazy calculating the the minimum friction force so that this ladder won't slip (brutal, but I did it). I am burnt out. How do I calculate N_1 here? It's the only force in the x direction other than friction, right? So by Newton's 2nd law the answer should just be friction = 1.5N_1, right?

2. Nov 7, 2009

### Tzim

Could you plz tell me wha t are the know data.

3. Nov 7, 2009

### Linus Pauling

... that picture has everything except that calculated minimum friction force, which is:

cot(theta) * (Lgm_2 + M_1gd - 0.5m_dLg * (Lgm_1 + Lgm_2)^-1