4. calculate the slope of the line in your graph of the square of the period of the spring vs. mass [slope = (y2 – y1)/(x2 – x1)]. robert hooke figured out the equation that describes the periodic motion of the spring. if you square both sides of the equation, you will find that the slope of the line is related to the spring constant (k). specifically, slope = 42/k. use your data to calculate the k of your spring.