Final answer:
The mass of an electron moving with a speed of 5.00*10^9 cm/sec is 9.11 x 10^(-31) kg.
Step-by-step explanation:
The mass of an electron moving with a speed of 5.00*10^9 cm/sec can be calculated using the relativistic equation E = mc^2, where E is the energy, m is the mass, and c is the speed of light. Since we have the speed of the electron, we can calculate its kinetic energy using the equation E = (1/2)mv^2, where m is the mass and v is the velocity. Equating the two expressions for energy and solving for m, we get m = E /(c^2/v^2 - 1). Substituting the given values, we get m = 9.11 x 10^(-31) kg, which corresponds to option b.