答案:A
—Who's won the first prize in the competition?
—Henry _______. He has ______ it for a week.[ ]
A. is; won
B. is; got
C. has; had
D. has; been given
如图所示,楔形木块静置于水平粗糙地面上,斜面与竖直墙之间放置一表面光滑的铁球,斜面倾角为θ,球的半径为R,球与斜面接触点为A.现对铁球施加一个水平向左的力F,F的作用线通过球心O,若缓慢增大压力F,在整个装置保持静止的过程中( )
A.任一时刻竖直墙对铁球的作用力都大于该时刻的水平外力F
B.斜面对铁球的作用力缓慢增大
C.斜面对地面的摩擦力保持不变
D.地面对斜面的作用力缓慢增大