【单选题】Earth's Inner Core Scientists have long struggled to understand what lies at the planet's center. Direct observation of its center is impossible, so researchers must(51) to other evidence. In 1889, a ...
【单选题】A hollow circular shaft with the ratio of the inner diameter to the outer diameter of α=d/D has torsion deformation due to the torques exerted at the two ends. Make the value of α be 0, 0.5, 0.6, and ...