|MadSci Network: Physics|
Dear Anonymous, The VOLUME of the balloon might be calculated by approximating its shape e.g. by a half-sphere + a cone, or, since it certainly has cylindrical symmetry, dividing its shape into "slices" which are considered as flat cylinders of varying diameter according to the silhouette of the balloon. In order to lift a mass, the buoyant force has to be at least slightly higher in magnitude than the weight (m times g) of the mass. Given that force equals counter-force, the excess buoyant force accelerates the mass upwards with acceleration a: the total force is thus m times (g+a). This is probably what you mean by "tension" in the string. Strictly speaking, tension is force per unit cross-section (of the string). I let you work out yourself what happens if the buoyant force becomes less than (m times g). Good flight W. Sieber
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