Can a 90 pound child exert enough force to rock a full size school bus?
If the bus is moving in traffic, the kid’s movements are insignificant. If the bus is standing still, it might be possible for one kid to used timed movements (like pumping your legs on a playground swing) to excite the natural frequency of the bus’s suspension — assuming all the other kids are sitting still. Even then it would be a small effect — the bus wouldn’t rock very much.
