Q. A barbell consists of two small balls, each with mass 600 grams (0.6 kg), at the ends of a very low mass rod of length d = 20 cm (0.2 m). The center of the barbell is mounted on the end of a low mass rigid rod of length b = 0.3 m, and this rod rotates clockwise with angular speed 140 rad/s. In addition, the barbell rotates clockwise about its own center, with an angular speed 120 rad/s.
Q. A 2.0 kg rock initially at rest loses 404 J of potential energy while falling to the ground. Assume that air resistance is negligible.
Calculate the kinetic energy that the rock gains while falling.