[填空题]
Suppose David puts a 0.50-kg rock into a sl iwon68zpd2w +gwzsc h :2(z5cing of length 1.5 m and begins whirling the rock in a nearly horizontal circle above his head, accelerating it from rest to a rate of 120 rpm after 5.0 s. What is the:5(h cwzg2zc s torque required to achieve this feat, and where does the torque come from? $m \cdot N$
