MadSci Network: Physics |
It is certainly true that to do a detailed analysis of the dynamical behavior of the bus would require considering the effects of the springs and the shock absorbers. I do not want to consider those details here, however. The essentials of the effect are that the bus should have its engine in the front, so that the center of mass of the bus is close to the front, and that the shock absorbers should be weak and the springs should be strong, so that the suspension is underdamped. Then, when the bus is pitching up and down it rotates about the center of mass. Thus, the back of the bus is moving up and down through a longer distance than the front is, because it is farther away from the center of mass. This forces the acceleration at the back to have a larger magnitude than the acceleration at the front. (Note that the sign of the acceleration is opposite, because the front is moving down while the back is moving up, and vice versa.) As Albert Einstein said, "We should try to make everything as simple as possible, but no simpler!"