[填空题]
The forearm in Fig. a,ulf;5 0zd (v-ktgxt :2xx7:cf fk6khk c;x o8–45 accelerates a 3.6-kg ball at 7 $m/s^2$ by means of the triceps muscle, as shown. Calculate
(a) the torque needed, $m \cdot N$
(b) the force that must be exerted by the triceps muscle. Ignore the mass of the arm. N