understanding experimental data generations of physics students have learned to estimate spring constants using an experimental apparatus similar to that pictured here the basic idea is to estimate the force stored in the spring by measuring the displacement caused by exerting known force on the spring we start with spring with no weight on itand measure the distance to the bottom of the spring from the top of the stand we then hang known mass on the springwait for it to stop movingand again measure the distance from the bottom of the spring to the top of the stand the difference between the two distances then becomes the value of in hooke' law we know that the forcefbeing exerted on the spring is equal to the massmmultiplied by the acceleration due to gravityg ( / is pretty good approximation of on this planet)so we substitute * for by simple algebra we know that -( * )/ supposefor examplethat kg and mthen ! ! !/=- !/ according to this calculationit will take newtons of force to stretch the spring one meter this would all be well and good if we had complete confidence in our ability to conduct this experiment perfectly in that casewe could take one measurementperform the calculationand know that we had found unfortunatelyexperimental science hardly ever works this wayand we could be sure that we were operating below the elastic limit of the spring more robust experiment is to hang series of increasingly heavier weights on the springmeasure the stretch of the spring each timeand plot the results the newtonwritten nis the standard international unit for measuring force it is the amount of force needed to accelerate mass of one kilogram at rate of one meter per second per second slinkyby the wayhas spring constant of approximately /