Question:

Which pair of physical quantities have same dimensional formula?

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Pressure, stress, and modulus of elasticity all have the same dimensional formula \(ML^{-1}T^{-2}\).
  • Torque and momentum
  • Surface tension and tension
  • Pressure and modulus of elasticity
  • Force constant and Planck's constant
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The Correct Option is C

Solution and Explanation

We need to identify the pair having the same dimensional formula. Pressure is defined as: \[ \text{Pressure}=\frac{\text{Force}}{\text{Area}}. \] The dimensional formula of force is: \[ [F]=MLT^{-2}. \] The dimensional formula of area is: \[ [A]=L^2. \] Therefore, \[ [\text{Pressure}]=\frac{MLT^{-2}}{L^2}. \] \[ [\text{Pressure}]=ML^{-1}T^{-2}. \] Now, modulus of elasticity is defined as: \[ \text{Modulus of elasticity}=\frac{\text{Stress}}{\text{Strain}}. \] Strain is dimensionless. So, \[ [\text{Modulus of elasticity}]=[\text{Stress}]. \] Stress is: \[ \text{Stress}=\frac{\text{Force}}{\text{Area}}. \] Therefore, \[ [\text{Stress}]=ML^{-1}T^{-2}. \] Hence, \[ [\text{Modulus of elasticity}]=ML^{-1}T^{-2}. \] Thus, pressure and modulus of elasticity have the same dimensional formula.
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