You'd better put your heart into study. You see, the ________ you are, the ______ progress (进步) you'll make.
A:careful, much
B:more careful, more
C:most careful, most
D:carefully, many
如图所示,水平桌面上放一个重2N,底面积为60cm2的杯子,杯内盛有20N的水,水深30cm,求:
(1)水对杯底的压力和压强;
(2)杯子对桌面的压力和压强.