The force required to stretch a spring varies with the distance as shown in the figure. If the experiment is performed with the above spring of half length, the line OA will

When the length of spring is halved, its spring constant will becomes double.     (because k∝1x∝1L∴k∝1L)Slope of force displacement graph gives the spring constant (k) of spring.If k becomes double then slope of the graph increases i.e. graph shifts towards force-axis.