An airplane will not be in equilibrium _______ .
A.in straight-and-level unaccelerated flight
B.when it is stationary on the ground
C.during a stabilized climb
D.when it is accelerating in calm air
正确答案是D
An airplane will not be in equilibrium _______ .
A.in straight-and-level unaccelerated flight
B.when it is stationary on the ground
C.during a stabilized climb
D.when it is accelerating in calm air
正确答案是D