[填空题]
The forearm in Fig. 8–45 acvxsu cm5 -z3pavu;rcea 2 eu2/7cmo ,/cr7 k809 nu5 1rdhhsix/frux3b elerates 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