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Most Important Selected Qs for JEE AdvancedPhysicsElectrostatics

A positive charged sphere of mass m =5 ~kg is attached by a spring of force constant K =10^4 ~N / m . The sphere is tied with a thread so that the spring is in its natural length. Another identical, negatively charged sphere is fixed to the floor, vertically below the positively charged sphere as shown in figure. Initial seperation between spheres is x₀=0.5 ~m . Now thread is burnt and maximum elongation of the sprin

Correct answer

4

Step-by-step solution

aligned & K =10^4 ~N / m ; m =5 ~kg & U_i= -k q^2 (0.5) & U_f= -k q^2 0.4 -m g(0.1)+ 1 2 k x^2 & U _ i + k _ i = U _ f +k f_ f⁻ ( kq ^2 )(2)= kq ^2(2.5)+ mg (0.1)- 1 2 k x^2 & 1 2 k x^2= k q^2 2 + mg (0.1) & 1 2 (10^2 ) ( 1 100 )= (9 10^9 ) q^2 2 + 45 2 590 10^9 =q^2 & q ^2= 5 2 10^9 =10⁻⁸ =100 C 25=100 =4 aligned

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