1、一个装有半杯水的杯子放弹簧测力计上示数4.9N,用线吊一物体全没在水杯中,不与杯接触,示数5.88N,沉底后示数7.

(1)G=G0+G1
G1=G-G0
=7.84N-4.9N
=2.94N
G1=mg
m=G1/g=2.94N/(9.8N/kg)
=0.3kg
G'=5.88N-4.9N
=0.98N
又G'=G1-F
F=G1-G'
=2.94N-0.98N
=1.96N
F=ρgV
V=F/ρg
=1.96N/(9.8N/KG*1000KG/M3)
=2*10的-4次方 M3
ρ=m/V
=0.3kg/ 2*10的-4次方 M3
=1500kg/M3
(2)因为木块漂浮,所以G=F
ρ木gv木＝ρ水gv排
ρ木/ρ水＝v排/v木
＝（1-1/5）/1
＝4/5
ρ木＝4/5ρ水
＝800kg/ M3
P=ρgh
ΔP=ρgΔh ( Δ表示变化量 )
Δh=ΔP/ρg
＝58.8Pa/(1000kg/m3*9.8N/kg)
=0.006m