Arehimedes' Principle A spherical buoy has a radius of 1 $\mathrm{m}$ and a density one-fourth that of seawater. By Archimedes' Principle, the weight of the displaced water will equal the weight of the buoy.
. Let $x=$ the depth to which the buoy sinks.
. Let $d=$ the density of seawater.
$\cdot$ Let $r=$ the radius of the circle formed where buoy, air, and water meet. See the figure below. Notice in the figure that $r^{2}=1-(1-x)^{2}=2 x-x^{2},$ and recall from geometry that the volume of submerged spherical cap is $$V=\frac{\pi x}{6} \cdot\left(3 r^{2}+x^{2}\right)$$
(a) Verify that the volume of the buoy is 4$\pi / 3$ .
(b) Use your result from (a) to establish the weight of the buoy as $\pi d / 3 .$
(e) Prove the weight of the displaced water is $\pi d \cdot x\left(3 r^{2}+x^{2}\right) / 6 .$
(d) Approximate the depth to which the buoy will sink.