Uniform, identical bricks \(20 \mathrm{~cm}\) long are stacked so that \(4.0 \mathrm{~cm}\) of each brick extends beyond the brick beneath, as shown in Figure 8.14a. How many bricks can be stacked in this way before the stack falls over?

THINKING IT THROUGH. As each brick is added, the center of mass (or center of gravity) of the stack moves to the right. The stack will be stable as long as the combined center of mass (CM) is over the base of support - the bottom brick. All of the bricks have the same mass, and the CM of each is located at its midpoint. So the horizontal location of the stack's CM must be computed as bricks are added until the CM extends beyond the base.