Question

What is the final speed of a free electron accelerated from rest through a potential difference of -120 V? The mass of the electron is 9.11x10-31kg. You need to express the speed in km/s.

You should round your answer to an integer, indicate only the number, do not include the unit.

Answer 1

The final speed of the electron is 6,497 km/s

Step-by-step explanation:

Given;

mass of the electron, m = 9.11 x 10⁻³¹ kg

electron potential, V = -120 V

Apply work energy theorem;

¹/₂mv² = eV

Where;

v is the final speed of the electron

e is the charge of the electron, = 1.602 x 10⁻¹⁹ C

`v = \sqrt{(2eV)/(m) }\\\\v = \sqrt{(2(1.602*10^(-19))(120))/(9.11*10^(-31)) }\\\\v = 6496473.75 \ m/s\\\\v = 6,497 \ km/s`

Therefore, the final speed of the electron is 6,497 km/s