Bulk Modulus of elasticity is one of the measures of mechanical properties of solids. Other elastic moduli are Young’s modulus and Shear modulus. Bulk modulus defines the ability of a material to resist deformation in terms of volume change, when subject to compression under pressure.

It is given by the ratio of pressure applied to the corresponding relative decrease in volume of the material. The relation is given below.

\(K = -V\frac{dP}{dV}\)

where,

K is the Bulk Modulus of the material expressed as \(N/m^{2}\)

dP is the change in pressure applied

dV is the change in volume of the system

V is volume of the system

Bulk modulus gives us a measure of how incompressible a solid is, as in, the more the value of K for a material, higher is its nature to be incompressible. For example, the value of K for steel is \(1. 6 \times 10^{11}\,N/m^{2}\)

K for steel is more than three times the value of Kfor glass. This implies is glass is more compressible than steel. Quite obvious. Try finding the Bulk Modulus value for diamond and comparing it with the value of steel and glass.

Consider this situation. You go deep sea diving into the Mariana Trenches. This is the following information you have in hand.

Bulk Modulus of Bone = \(1.5 \times 10^{10}\,N/m^{2}\)

Atmospheric Pressure = \(1.01 \times 10^{5}\,N/m^{2}\)

Pressure at deep point = \(1.09 \times 10^{8}\,N/m^{2}\)

You have two tasks;

- Find out what the value of \(\frac{dV}{V}\)
will be for your bones - Appreciate atmospheric pressure because you don’t die here

The concept of Bulk Modulus is used mostly in liquids. In solids, Young’s modulus is used commonly and the value of K varies in gases, as they are extremely compressible. Explore more about physics formulas and calculators with our expert faculty, here at BYJU’S.

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