Radioactive carbon-14 decays into nitrogen-14. a piece of carbon-14 that originally had a mass of 1 kilogram is later found to have a mass of 0. kilogram. how much energy was released?

Asolid cylinder and a cylindrical shell have the same mass, same radius, and turn on frictionless, horizontal axles. the cylindrical shell has light-weight spokes connecting the shell to the axle. a rope is wrapped around each cylinder and tied to blocks of equal masses that are held the same height above the ground. both blocks are released simultaneously. the ropes do not slip. which block hits the ground first? or is it a tie?