[填空题]
Calculate the net torqu pien9+ 8is 1:bjmis40gubz8u(*6ov. yh ;d4 sy0hhpb q5bs el(db:wfe about the axle of the wheel shown in Fig. 8–39. Assume that a friction torquevb*syqpb05eh4dh yb:f(6s(w . hd;lo of 0.4 $m \cdot N$ opposes the motion. $m \cdot N$