[填空题]
The forearm in Fig. 4ld)6 r4x /c*t-9eu )igz 2yt8m kv(ayselimc 8–45 accelerates a 3.2jk6ywbtafm/w0 2l f;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