WAEC Physics 2011 Theory — Question 38

Question 38 of 39 from the West African Examinations Council (WAEC) Physics 2011 Theory paper, with the correct answer and a full explanation.

15(c)(iii) Calculate the speed of an emitted electron. (mass of electron = 9.1x10⁻³¹kg)

Model answer

Using K.E. = ½mv², v² = 2xK.E./m = (2x2.9x10⁻¹⁹)/9.1x10⁻³¹ = 6.46x10¹¹, so v = 8.04x10^5 m/s.

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