Q129 / 180 · COMEDK 2017 · Physics

Which one of the following is not a tunit of Young's modulus?

  • Correct answer
    A
    $\mathrm{Nm}^{-1}$
  • B
    $\mathrm{Nm}^{-2}$
  • C
    dyne $\mathrm{cm}^{-2}$
  • D
    Mega pascal

Solution

Young's modulus, $Y=\frac{\text { Stress }}{\text { Strain }}$ Here, strain is a dimensionless quantity and stress is measured in SI unit of $\mathrm{Nm}^{-2}$, dyne $\mathrm{cm}^{-2}$ or pascal. So, the Young's modulus has the same unit as stress. $\therefore \mathrm{Nm}^{-1}$ is not a unit of Young's modulus.

Hence, the correct answer is option: 'A'.

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