Suppose a diode consists of a cylindrical cathode with a radius of 6.200102 cm, mounted coaxially within a cylindrical anode with a radius of 0.5580...

Suppose a diode consists of a cylindrical cathode with a radius of 6.200×10−2 cm, mounted coaxially within a cylindrical anode with a radius of 0.5580 cm. The potential difference between the anode and cathode is 280 V. An electron leaves the surface of the cathode with zero initial speed (v_{rm initial} = 0). Find its speed v_final when it strikes the anode.