Question

Use conservation of energy please!!

An electron is initially at ground level, and the electric potential at that point is assumed to be exactly zero. The electron is immersed in a uniform electric field that points down with a magnitude of 4.4 x 10-11 N/C as well as Earth's gravitational field (9.8 N/kg, pointing down). Only gravity and the electric force have any effect in this problem. a) If the electron is given an initial upward velocity of 36 m/s, to what maximum height above b) c) d) ground level does it reach? What is the change in electric potential energy (final- initial) during this motion? How much work is done by the electric force during this motion? What is the voltage at the electron's maximum height?

Answer 1

(a) Using conservation of Energy u_i + k_i = u_f + k_f (0 + 0) + 1/2 m_e v_i^2 = (m g h + (-e) (E h)) + 1/2 m_e O^2 rightdoublearrow h = 1/2 times 9.1 times 10^-31 times 36^2/(9.1 times 10^-31 times 9.8) - (1.6 times 10^-19 times 4.4 times 10^-11) = 313.99 m \r\n (b) delta u_electric = q (v_f - v_i) = (-1 6 times 10^-19) (E h - 0) = -1.6 times 10^-19 times 4.4 times 10^-11 times 313.99 = -2.21 times 10^-27 J (c) Work done by electric force = -delta U_electric = 2.21 times 10^-27 J (d) Voltage at max height = E h = 1.38 times 10^-8 V