In the first figure, a block of mass m lies on a horizontal frictionless surface and is attached to one end of a horizontal spring (spring constant k) whose other end is fixed. The block is initially at rest at the position where the spring is unstretched (x = 0) when a constant horizontal force in the positive direction of the x axis is applied to it. A plot of the resulting kinetic energy of the block versus its position x is shown in the second figure. The scale of the figure's vertical axis is set by Ks= 7.0 J. (a) What is the magnitude of F ? (b) What is the value of k? x=0 Block F= 0 attached to spring -X o - (a) K. K (J) 0 0.5 1 1.5 2 x (m) (a) Number Units (b) Number Units