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An X-ray tube is run with a potential difference of 15 kV. What is the maximum possible speed of the electrons that hit the target?

1. 7.26 × 10⁷ m/s
2. 7.62 × 10⁷ m/s
3. 7.62 × 10⁷ cm/s
4. 7.26 × 10⁹ m/s

Correct answer: 7.26 × 10⁷ m/s

Solution

eV = (1/2)mv^2 -> v = sqrt(2eV/m) = sqrt(2*1.6e-19*15000/9.1e-31) = sqrt(5.27e15) ~ 7.26x10^7 m/s.

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