Question

三個(gè)同種材料的圓柱體放在水平桌面上，高度相同，其質(zhì)量關(guān)系是m_甲＞m_乙＞m_丙．如果對(duì)桌面的壓力分別為F_甲、F_乙、F_丙，對(duì)桌面的壓強(qiáng)分別為P_甲、P_乙、P_丙，那么（　�。�

A．F甲=F乙=F丙，P甲=P乙=P丙

B．F甲＞F乙＞F丙，P甲＞P乙＞P丙

C．F甲＞F乙＞F丙，P甲=P乙=P丙

D．F甲=F乙=F丙，P甲＞P乙＞P丙

Answer 1

已知m_甲＞m_乙＞m_丙所以G_甲＞G_乙＞G_丙，對(duì)桌面的壓力就等于重力，所以F_甲＞F_乙＞F_丙．
∵m=ρV，∴V_甲＞V_乙＞V_丙，又因?yàn)閂=Sh，∴S_甲＞S_乙＞S_丙，因?yàn)?span mathtag="math" >P=

F

S

=

mg

S

=

ρVg

S

=

ρShg

S

=ρgh，
∴P_甲=P_乙=P_丙．
故選C．