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Charge, Kinetic Energy

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5. Two metal plates are held at a potential difference of 40 volts, in a vacuum. A proton is released near the positive plate, and moves toward the negative plate under the influence of the electric field. A proton's mass is 1.67 * 10^-27 kg.

(A) Just before the proton hits the other plate, what is its kinetic energy? Express it either in Joules or electron volts. (Remember the work-energy principle.)

(B) What is the velocity of the proton just before it hits the negative plate?

6. Two uncharged metal balls, X and Y, stand on glass rods. A third ball, Z, carrying a positive charge, is brought near the first two, as shown. A conducting wire is then connected between X and Y. The wire is then removed, and ball Z is finally removed. When this is all done, which of the following is true?

(a) Balls X and Y are still uncharged.
(b) Balls X and Y are both charged positively.
(c) Balls X and Y are both charged negatively.
(d) Ball X is positive and ball Y is negative.
(e) Ball X is negative and ball Y is positive.

Explain your answer.

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Solution Preview

(a) From energy conservation, all electrical potential energy will be transferred into kinetic energy.

=> Ek = q*V =1.6e-19 * 40 = 6.4e-18 ...

Solution Summary

Step by step calculation and brief explanation.