1. A ball is thrown horizontally from a height of 30 m and hits the ground with a speed that is three times its initial speed. The initial speed of the ball is _(1)_ m/s.

10. Several objects (a hoop, a solid cylinder, a solid sphere, and a thin spherical shell) roll, without slipping down an incline of vertical height H, all starting from rest at the same moment. In addition a box slides down without friction. In what order do they reach the bottom of the incline?