A ladder is leaning against a vertical wall, and both ends of the ladder are at the point of slipping. The coefficient of friction between the ladder and the horizontal surface is μ1 = 0.265 and the coefficient of friction between the ladder and the wall is μ2 = 0.253. Determine the maximum angle with the vertical the ladder can make without falling on the ground.

Respuesta :

Answer:

[tex]\alpha =29.60[/tex]

Explanation:

Let the normal force of the wall on the ladder be N2 and the normal force of the ground on the ladder be N1.

Horizontal forces:

[tex]N_{2}= (u1)(N_{1})[/tex] [1]

Vertical forces:

[tex]N_1 + (u2)(N_{2})=m*g[/tex] [2]

Substitute [2] into [1]:

[tex]N_2 = (u1)*[m*g - (u2)(N_2)][/tex]

[tex]N_2= \frac{(u1)m*g}{[1 + (u1)(u2)]}[/tex] [3]

Torques about the point where the ladder meets the ground:

[tex]m*g(\frac{L}{2})sin\alpha= (N_2)(L)cos\alpha+(u2)(N_2)(L)sin\alpha[/tex]

[tex](\frac{1}{2})*m*g=(N_2)*cot\alpha+(u2)(N_2)[/tex]

[tex][1 + (u1)(u2) - 2(u2)(u1)]/2 [1 + (u1)(u2)]= [(u1)/[1 + (u1)(u2)]]cot\alpha[/tex]

tanα = [tex]\frac{2*(u1)}{1-u1*u2}[/tex]

[tex]\alpha =tan^{-1}*(\frac{2*0.265}{1-0.265*0.253})[/tex]

[tex]\alpha =tan^{-1}*(0.568)[/tex]

[tex]\alpha =29.60[/tex]