Calculate the buoyant force in air on a kilogram of lead (whose density is about 11 grams per cubic centimeter). The density of air is 1.3 10-3 grams per cubic centimeter. Remember that the buoyant force is equal to the weight of a volume of air that is equal to the volume of the object. (Compare with the weight mg of this much lead, which is 9.8 N.)
What formula should I use for this? I looked in the text book - but it didn't seem to help. I tried a few didfferent things, but nothing seemed to work. I'm more interested in knowing how to work this out than the answer and any help would be appreciated.
What formula should I use for this? I looked in the text book - but it didn't seem to help. I tried a few didfferent things, but nothing seemed to work. I'm more interested in knowing how to work this out than the answer and any help would be appreciated.
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The buoyant force = weight of the volume of air that is displaced by the lead. The volume of the displaced air is equal to the volume of the lead.
Density = mass/volume
Volume = mass/Density
For lead, mass = 1000 grams
Volume of lead = 1000 g/ 11 g/cc = 90.9 cc
Volume of displaced air = 90.9 cc
Mass of displaced air = 1.3 * 10^-3 g/cc * 90.9 cc = 1.1817 * 10^-1 g = 1.1817 * 10^-4 kg
Weight of displaced air = 1.1817 * 10^-4 * 9.8 = 1.158066 * 10^-3 N
The buoyant force = 1.158066 * 10^-3 N
Round as your instructor desires
Without rounding, buoyant force = (1.3 * 10^-3) * (1000/11) ÷ (1000) * (9.8)
Without rounding, buoyant force = 9.8 * 1.3 * 10^-3 ÷ 11
Density = mass/volume
Volume = mass/Density
For lead, mass = 1000 grams
Volume of lead = 1000 g/ 11 g/cc = 90.9 cc
Volume of displaced air = 90.9 cc
Mass of displaced air = 1.3 * 10^-3 g/cc * 90.9 cc = 1.1817 * 10^-1 g = 1.1817 * 10^-4 kg
Weight of displaced air = 1.1817 * 10^-4 * 9.8 = 1.158066 * 10^-3 N
The buoyant force = 1.158066 * 10^-3 N
Round as your instructor desires
Without rounding, buoyant force = (1.3 * 10^-3) * (1000/11) ÷ (1000) * (9.8)
Without rounding, buoyant force = 9.8 * 1.3 * 10^-3 ÷ 11