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My answer to a) is 1.14 * 10^-19 J, which is correct.An elecetron has a mass of 9.11 * 10^-31 kg. If it moves across a television picture tube at a speed of 5.0 * 10^5 m/s. Calculate:

a) it's kinetic energy

b)how many such electrons would transfer 1 J of energy to the screen.

My answer to b) is 1.14 * 10^19, which is not correct. The correct answer is 8.8 * 10^18. How did they get that? because if 1 electron has 1.14 * 10^-19 J then wont we need 1.14 * 10^19 electrons for 1 J ?