MCQ
Which of the following ratios express pressure?
  • A
    $\frac{\text{Force}}{\text{Area}}.$
  • B
    $\frac{\text{Energy}}{\text{Volume}}.$
  • C
    $\frac{\text{Energy}}{\text{Area}}.$
  • D
    $\frac{\text{Force}}{\text{Volume}}.$

Answer

  1. $\frac{\text{Force}}{\text{ Area}}.$

  2. $\frac{\text{Energy}}{\text{Volume}}.$

Explanation:

Let us first express the relation of pressure with other physical quantities one by one with the help of dimensional analysis.

We know that pressure,

  1. $\frac{\text{Force}}{\text{Area}}=\frac{[\text{MLT}^{-2}]}{[\text{L}^2]}=[\text{ML}^{-1}\text{T}^{-2}]$

So, this ratio express pressure (In fact this ratio actually represents pressure).

  1. $\frac{\text{Energy}}{\text{Area}}=\frac{[\text{ML}^{2}\text{T}^{-2}]}{[\text{L}^2]}=[\text{MT}^{-2}]$

Dimensions of this ratio are not same as pressure, so this ratio does not express pressure.

  1. $\frac{\text{Energy}}{\text{Volume}}=\frac{[\text{ML}^{2}\text{T}^{-2}]}{[\text{L}^3]}=[\text{ML}^{-1}\text{T}^{-2}]$

Dimensions of this ratio is the same as pressure, so this ratio also express pressure.

  1. $\frac{\text{Force}}{\text{Volume}}=\frac{[\text{ML}\text{T}^{-2}]}{[\text{L}^3]}=[\text{ML}^{-2}\text{T}^{-2}]$

Dimensions of this ratio are not same as pressure, so this ratio does not express pressure.

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