A) Consider a simply-supported, low-alloy steel shaft, ten feet in length and two inches in diameter. The shaft supports a single concentrated mass at its center. The weight of the concentrated mass is 0.6 kip. Estimate the critical speed of the shaft, expressed in rpm.
B) Consider a simply-supported, low-alloy steel shaft, ten feet in length and two inches in diameter. The shaft supports two equal concentrated masses, each located two feet from its center. The weight of each concentrated mass is 0.5 kip. Estimate the critical speed (first natural frequency) of the shaft, expressed in rpm.