An object is placed on a board. The coefficient of static friction between the object and the board is 0.40. One end of the board is slowly raised until the object begins to slide. The angle that the board makes when the object begins to slide is
A) 16°.
B) 22°.
C) 74°.
D) unknown; the answer cannot be determined without knowing the mass of the object.

Question

Quizplus · Accepted Answer

The angle at which the object begins to slide is determined by the coefficient of static friction, $\mu_s = \tan(\theta)$. Solving for $\theta$ gives $\theta = \tan^{-1}(0.40)$, which is approximately 22°. The mass of the object is not required to determine this angle.

An Object Is Placed on a Board