A box of mass m sliding with an initial speed of vi on a rough horizontal surface runs into a fixed spring of elastic constant k, compressing it a distance x1 from its relaxed position while momentarily coming to rest. Write down the equation that best represents the energy conversion during the process of the box compressing the spring?

Light from two different sources are incident upon the same side of a polarizing filter. light from one source is polarized with total intensity ip, while light from the other source is unpolarized with total intensity iu. as you rotate the polarizing filter through 360 degrees, the intensity of the transmitted light on the other side varies by a factor of 9. what is the relative intensity of the initial polarized source to the unpolarized source, or ip/iu?