Assume the shape of a helium balloon to be a sphere of radius, r, equal to 9 m, at standard sea level conditions. the volume, v, of a sphere is expressed as v = (4pi/3)r^3. note the molecular weight of he is mhe = 4 kg/kmol and for air, mair = 29 kg/kmol.
a. calculate the density of the helium, phe, inside balloon and the weight of the balloon, w,
assuming the material of the balloon is negligible.
b. calculate the balloon's buoyant force, fb.
c. what is the name of the principle by which the helium balloon derives its lift force?