Railways Technical Ability Instrument Mechanical Question Bank Instrument Mechanical

  • question_answer For discharge 'Q' the specific speed of a pump is\['{{N}_{s}}'.\] For half discharge with the same head, the specific speed will be:

    A) \[{{N}_{s}}\]                           

    B) \[\sqrt{2}{{N}_{s}}\]

    C) \[\frac{{{N}_{s}}}{\sqrt{2}}{{N}_{s}}\]                       

    D) \[2{{N}_{s}}.\]

    Correct Answer: B

    Solution :

    For a pump, \[{{N}_{s}}=\frac{N\sqrt{Q}}{{{H}^{3/4}}}\] \[{{N}_{s}}\propto \sqrt{Q}\] \[\frac{{{N}_{s2}}}{{{N}_{s1}}}=\frac{\frac{\sqrt{Q}}{2}}{Q}\] \[{{N}_{s2}}={{N}_{s2}}\frac{{{N}_{s}}}{\sqrt{2}}\]

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