(a) A physics lab instructor is working on a new demonstration. She attaches two identical copper spheres with mass m = 0.180 g to cords of length L as shown in the figure. A Both spheres have the same charge of 6.80 nC, and are in static equilibrium when = 4.95°. What is L (in m)? Assume the cords are massless. 0.150 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 0, and use this expression in your Coulomb force equation. m (b) What If? The charge on both spheres is increased until each cord makes an angle of 0 = 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? 13.6 ☑ 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

A proton moves at 5.20 x 105 m/s in the horizontal direction. It enters a uniform vertical electric field with a magnitude of 8.40 × 10³ N/C. Ignore any gravitational effects. (a) Find the time interval required for the proton to travel 6.00 cm horizontally. 1.15e-7 ☑ Your response differs significantly from the correct answer. Rework your solution from the beginning and check each step carefully. ns (b) Find its vertical displacement during the time interval in which it travels 6.00 cm horizontally. (Indicate direction with the sign of your answer.) 5.33e-3 ☑ Your response is off by a multiple of ten. mm (c) Find the horizontal and vertical components of its velocity after it has traveled 6.00 cm horizontally. | ↑ + jkm/s

A proton moves at 5.20  105 m/s in the horizontal direction. It enters a uniform vertical electric field with a magnitude of 8.40  103 N/C. Ignore any gravitational effects. (a) Find the time interval required for the proton to travel 6.00 cm horizontally. (b) Find its vertical displacement during the time interval in which it travels 6.00 cm horizontally. (Indicate direction with the sign of your answer.)