What is albert einstein’s contribution to the understanding of nuclear energy?

he proposed that matter can be converted to energy and vice versa.
he first discovered that nuclear-reaction products are lighter than the reactants.
he developed the use of nuclear reactions to generate electricity.
he demonstrated that a uranium nucleus splits and releases neutrons.

Four objects each with charge +2.0×10−7c are located at the corners of a square whose sides are 2.0 m long. part a what quantities can be determined using this information? check all that apply. the electric force on a charged object placed at the center of the square. the mass of each object. the total electric potential energy of the system consisting of the four charged objects. part b find the electric force on a charged object placed at the center of the square.