Question

calc the buoyant force on a 2 L helium balloon

Answer 1

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.

Answer 2

Correction:
2000g = 2kg = mass.

F = mg = 2kg * 9.8N/kg = 19.6 N.

Answer 3

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.