[填空题]
A 7650$-\mathrm{kg}$ helicopter accelerates upward at 0.80 $\mathrm{~m} / \mathrm{s}^{2}$ while lifting a 1250$-\mathrm{kg}$ frame at a construction site, Fig. 4-62.
(a) What is the lift force exerted by the air on the helicopter rotors?
(b) What is the tension in the cable (ignore its mass) that connects the frame to the helicopter?
(c) What force does the cable exert on the helicopter?
