A Toolbox, of Mass M, Is Resting on a Flat $\theta$

Multiple Choice

A toolbox, of mass M, is resting on a flat board, as shown in Figure 4-5. One end of the board is lifted up until the toolbox just starts to slide.

The angle $\theta$ that the board makes with the horizontal, for this to occur, depends on the

A) coefficient of kinetic friction, _k.
B) coefficient of static friction, _s.
C) acceleration of gravity, g.
D) mass, M.
E) all of the above quantities.