A favorite class demonstration by Hewitt is lying on his back with a blacksmith’s anvil pl...

A favorite class demonstration by Hewitt is lying on his back with a blacksmith’s anvil placed on his chest. When an assistant whacks the anvil with a strong sledge-hammer blow, Hewitt is not injured. How is the physics here similar to that illustrated in Figure 1.8?

FIGURE 1.8

Why does the blow of the hammer not harm her?