答案:C
竖直向上抛出一个排球,排球在上升和下降过程中都受到空气阻力作用,阻力小于重力且大小不变.若排球上升时受到的合力的大小为F1,下降时受到的合力的大小为F2,则( )
A.F1>F2
B.F1<F2
C.F1=F2
D.无法判断
—_____ will she finish her project?
—In about 2 hours. [ ]
A. How long
B. When
C. How soon
D. Hoe often