The Pacific Science Center in Seattle, Washington, has an exhibit in which patrons can r...

The Pacific Science Center in Seattle, Washington, has an exhibit in which patrons can ride a bicycle around a narrow track high above the ground. A large concrete block hangs beneath the bike on a long bar that is fastened rigidly to the bike’s frame. The following picture shows Greg’s wife Sandra riding the bike without much concern for her safety. Why is this exhibit safe?