下列有关注水泵出口说法正确的是()。
A.注水泵出口设有单向阀
B.注水泵出口不设单向阀
C.运行时注水泵出口压力是恒定不变
D.运行时注水泵出口压力是脉冲式变化的
参考答案:A, D
-- Would she mind playing against her former teammates?
-- __ She is willing to play against any tough players.
A.I think so.
B.I'm not surprised.
C.Of course.
D.Not likely!
(14分)一小石块从空中自由下落h=5m后,掉入淤泥,落到淤泥底时速度恰好为零,全过程共用时t=1.2s。假设石块在淤泥中做匀减速直线运动,且g=10m/s2,则:
(1)小石块掉入淤泥前的瞬时速度大小为多少;
(2)石块陷入淤泥的深度d及此过程石块的加速度的大小