Imagine putting a single and a double brick on a flat board, as in Figure 10.40, and then slowly raising one end of the board.

(a) Does the single brick begin to slide before, after, or at the same time as the double brick?

(b) Once the bricks start sliding, is the acceleration of the double brick larger than, equal to, or smaller than that of the single brick?

Figure 10.40 On a rough surface, a single brick slides more easily than a double brick. The harder two surfaces press against each other, the larger the effective contact area, and consequently the stronger the bond between the surfaces. hb v = 0 Fi hb