posted by chris .
calc the buoyant force on a 2 L helium balloon
Buoyant force is the wt. of the water displaced.
2L = 2000cm^3.
Density of water = 1g/cm^3.
F = 2000cm^3 * 1g/cm^3 = 2000 Grams.
2000g = 2kg = mass.
F = mg = 2kg * 9.8N/kg = 19.6 N.
I got that far too, but the answer is supposed to be 2.53x10^-3 N. I am not given anything else but the volume.