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48.

48. || A plastic rod with linear charge density A is bent into the CALC quarter circle shown in FIGURE P2143. We want to nd the electric eld at the origin. 3. Write expressions for the x- and y-components of the electric field at the origin due to a small piece of charge at angle 3. be Write, but do not evaluate. definite integrals for the x and y-cornponents of the net electric field at the origin. c. Evaluate the integrals and write Em in component form. 53. III The two parallel plates in FIGURE P23.53 are 2.0 cm apart and the electric field strength between them is 1.0 X 10* N/C. An electron is launched at a 45 angle from the positive plate. What is the maximum initial speed vo the electron can have without hitting the negative plate?55. III A positron is an elementary particle identical to an electron except that its charge is +e. An electron and a positron can rotate about their center of mass as if they were a dumbbell connected by a massless rod. What is the orbital frequency for an electron and a positron 1.0 nm apart? 59. II In a classical model of the hydrogen atom. the electron orbits the proton in a circular orbit of radius 0.053 nm. What is the or- bital frequency? The proton is so much more massive than the electron that you can assume the proton is at rest. 49. II An infinite plane of charge with surface charge density 3.2 uC/m has a 20-cm-diameter circular hole cut out of it. What is the electric field strength directly over the center of the hole at a distance of 12 cm? Hint: Can you create this charge distribution as a superposition