Question

A light spring of constant k = 95.0 N/m is attached vertically to a table (figure (a)). A 2.70-g balloon is filled with helium (density = 0.179 kg/m3) to a volume of 4.00 m3 and is then connected to the spring, causing the spring to stretch as shown in figure (b). Determine the extension distance L when the balloon is in equilibrium. (The density of air is 1.29 kg/m3.)

m

Answer 1

bouyant force=weight of air displaced-weight of balloon.
= denAir*4m^3-densityH3*4m^3 -.027(9.8)
= 4(1.29kg-.179kg) - .027g=4*1.11 N-.027*9.8N

stretch=force/k=bouyantforceabove/95N/m