JEE Main & Advanced Physics NLM, Friction, Circular Motion Question Bank Self Evaluation Test - Laws of Motion

  • question_answer
      A balloon with mass 'm' is descending down with an acceleration 'a' (where a < g). How much mass should be removed from it so that it starts moving up with an acceleration 'a'?

    A) \[\frac{2ma}{g+a}\] 

    B) \[\frac{2ma}{g-a}\]

    C) \[\frac{ma}{g+a}\]

    D) \[\frac{ma}{g-a}\]

    Correct Answer: A

    Solution :

    [a] Let up thrust of air be\[~{{F}_{a}}\]then For downward motion of balloon \[{{F}_{a}}=mg-ma\] \[mg-{{F}_{a}}=ma\] For upward motion \[{{F}_{a}}-\left( m-\Delta m \right)g=\left( m-\Delta m \right)a\] Therefore \[\Delta m=\frac{2ma}{g+a}\]


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