JEE MAIN - Physics (2021 - 26th February Morning Shift - No. 17)
The normal density of a material is $$\rho$$ and its bulk modulus of elasticity is K. The magnitude of increase in density of material, when a pressure P is applied uniformly on all sides, will be :
$${{\rho K} \over P}$$
$${{PK} \over \rho }$$
$${{\rho P} \over K}$$
$${K \over {\rho P}}$$
Explanation
Bulk modulus $$K = {{ - \Delta P} \over {{{\Delta v} \over v}}} = {{ - \Delta Pv} \over {\Delta v}}$$
We know, $$\rho = {M \over V}$$
So, $${{ - \Delta \rho } \over \rho } = {{\Delta v} \over v}$$
$$K = {{ - \Delta P} \over {\left( { - {{\Delta \rho } \over \rho }} \right)}} = {{\rho \Delta P} \over {\Delta \rho }}$$
$$\Delta \rho = {{\rho \Delta P} \over K}$$
$$\Delta \rho = {{\rho P} \over K}$$
We know, $$\rho = {M \over V}$$
So, $${{ - \Delta \rho } \over \rho } = {{\Delta v} \over v}$$
$$K = {{ - \Delta P} \over {\left( { - {{\Delta \rho } \over \rho }} \right)}} = {{\rho \Delta P} \over {\Delta \rho }}$$
$$\Delta \rho = {{\rho \Delta P} \over K}$$
$$\Delta \rho = {{\rho P} \over K}$$
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