[填空题]
(a) Find the force req c0o .i7gsmu.v4r7a,+ptsw 8um j3efpuired t+:ligv z-h+g;0yms+srr :d yao give a helicopter of mass M an acceleration of 0.10 zrr+;a -+0+sgh mys:v dyi lg:g upward. Mg
(b) Find the work done by this force as the helicopter moves a distance h upward. Mgh
