A force of 2 pounds is required to hold a spring stretched 0.2 feet beyond its natural length. How much work (in foot-pounds) is done in stretching the spring from its natural length to 0.6 feet beyond its natural length?

Which of the following will cause an induced current in a coil of wire? the constant field of the earth passing through the coil a magnet resting near the coil a magnet being moved into or out of the coil a wire carrying a constant current near the coil