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(a) A physics lab instructor is working on a new demonstration. She attaches two identical metal spheres with mass m = 0.190 g to strings of length L as shown in the figure. m L m Both spheres have the same charge of 6.40 nC, and are in static equilibrium when Assume the strings are massless. = 4.95°. What is L (in m)? -1.268 Draw a free-body diagram, apply Newton's second law for a particle in equilibrium to one of the spheres. Find an equation for the distance between the two spheres in terms of L and 8, and use this expression in your Coulomb force equation. m (b) What If? The charge on both spheres is increased until each string makes an angle of 8 = 9.90° with the vertical. If both spheres have the same electric charge, what is the charge (in nC) on each sphere in this case? 24.3 Use the same reasoning as in part (a), only now, use the length found in part (a) and the new angle to solve for the charge. nC