ISRO Mechanical & Aerospace 2018 - Question 75

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Topic: Theory of Machines

If the length of the cantilever beam is reduced to 1/4th, the natural frequency of the mass M at the end of this cantilever beam of negligible mass will be increased by a factor of

  • A. 2
  • B. $\sqrt{8}$
  • C. 4
  • D. 8

Answer: D. 8

Explanation: Deflection delta = (Mg*L³)/(3EI). Natural frequency f is proportional to 1/$\sqrt{delta}$, which means f is proportional to 1/L^(3/2). f2/f1 = (L1/L2)^(3/2) = (L / (L/4))^(3/2) = 4^(3/2) = 8.

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