Question

一平底玻璃杯放在水平面上,内装150g的水,杯子与桌面的接触面积是10cm2.

若桌面所受玻璃杯压强是2700Pa,求玻璃杯的质量.(10N/kg)
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Answer 1

杯底所受水的压强：
p=ρgh=1000kg/m3×10N/kg×0.12m=1200Pa，
水对杯底的压力：
F=ps=1200Pa×10×10-4m2=1.2N；
（2）玻璃杯对水平支持面的压力：
F=G杯+G水=1.2N+m杯g=1.2N+0.15kg×10N/kg=2.7N，
玻璃杯对桌面的压强
p′=F S =2.7N /10×10负4次方m2
=2.7×103Pa．
答：（1）水对杯底的压强和压力分别为1200Pa、1.2N；
（2）桌面所受玻璃杯的压强为2.7×103Pa．