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A thin homogeneous rod of mass m and length lambda is free to rotate in vertical plane about a horizontal axle pivoted at one end of the rod. A small ball of mass m and charge q is attached to the opposite end of this rod. The whole system is positioned in a constant horizontal electric field of magnitude E equals fraction numerator m g over denominator 2 q end fraction The rod is released from shown position from rest.

What is the angular acceleration of the rod at the instant of releasing the rod?

  1. fraction numerator 8 g over denominator 9 t end fraction  
  2. fraction numerator 3 g over denominator 2 t end fraction  
  3. fraction numerator 9 g over denominator 8 t end fraction  
  4. fraction numerator 2 g over denominator 9 t end fraction  

The correct answer is: fraction numerator 9 g over denominator 8 t end fraction



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