JEE Main & Advanced Physics Mathematical Tools, Units & Dimensions Question Bank Mock Test - Units Dimenstions and Measurment

  • question_answer
    A body travels uniformly a distance of\[(S+\Delta S)\] in a time \[(t\pm \Delta t)\]. What may be the condition so that body within the error limits move with a velocity \[(\frac{S}{t}\pm \frac{\Delta S}{\Delta t})\]?

    A) \[\frac{\Delta t}{t}+\frac{S(\Delta t)_{{}}^{2}}{(\Delta S)t_{{}}^{2}}=\pm 1\]

    B) \[\frac{\Delta t}{t}+\frac{S\Delta t_{{}}^{{}}}{\Delta St_{{}}^{{}}}=\pm 1\]

    C) \[\frac{\Delta t}{t}+\frac{(\Delta S)t_{{}}^{{}}}{S(\Delta t)_{{}}^{{}}}=\pm 1\]         

    D) \[\frac{\Delta t}{t}+\frac{S_{{}}^{2}\Delta t_{{}}^{{}}}{(\Delta S)_{{}}^{2}t_{{}}^{{}}}=\pm 1\]

    Correct Answer: A

    Solution :

    [a] \[V=\frac{S}{t}\] \[\Delta V=\frac{1}{t}.\frac{\partial s}{\partial s}.\Delta S+\frac{S}{{{t}^{2}}}\Delta t=\left( \frac{\Delta S}{t}+\frac{S\Delta t}{{{t}^{2}}} \right)\] So \[\frac{\Delta S}{t}+\frac{S\Delta t}{{{t}^{2}}}=\frac{\Delta S}{\Delta t}.\frac{\Delta t}{t}+\frac{(\Delta S).S(\Delta {{t}^{2}})}{(\Delta S).{{t}^{2}}(\Delta t)}\] Or         \[\frac{\Delta S}{\Delta t}\left[ \frac{\Delta t}{t}+\frac{S{{(\Delta t)}^{2}}}{(\Delta S){{t}^{2}}} \right]=\pm \frac{\Delta S}{\Delta t}\](given) So, \[\frac{\Delta t}{t}+\frac{S{{(\Delta t)}^{2}}}{(\Delta S){{t}^{2}}}=\pm 1\]          


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