Answer:
To measure diameter of a spherical body using Vernier Callipers.A small, movable auxiliary graduated scale attached parallel to a main graduated scale and calibrated to indicate fractional parts of the subdivisions of the larger scale.It is useful tool to measure spherical body.Diameter of a sphere=d = 2 * r , Surface area of a sphere: A = 4 * π * r² , Volume of a sphere: V = 4/3 * π * r³ , Surface to volume ratio of a sphere: A / V = 3 / r .