當(dāng)浸入 1/2 體積時(shí)所受的浮力大小為：F浮= G - T = 14.7N - 9.8N = 4.9N

所以,當(dāng)全部浸入時(shí)所受的浮力大小為：= 2 × 4.9N = 9.8N

此時(shí)彈簧秤的拉力：T = G - F浮 = 14.7N - 9.8N = 4.9N

因?yàn)?F浮 = ρ水× V物×g = 10^3kg/m^3 × V物 × 9.8N/kg = 9.8N

所以,V物= 10^-3 m^3 = 1L

ρ物 = G/g ÷ V物 = 14.7N/9.8N/kg ÷ 1L = 1.5kg/L = 1.5×10^3kg/m^3

浸沒(méi)到酒精中時(shí)所受到的浮力：F'浮= ρ酒× V物×g = 0.8kg/L× 1L × 9.8N/kg = 7.84N

彈簧秤的讀數(shù)：T = G - F'浮 = 14.7N - 7.84N ∽ 6.9N