Chapter 7, Problem 30P

In Fig. 7-10a, 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 $\stackrel{\to }{F}$ 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 Fig. 7-36. The scale of the figure’s vertical axis is set by K_s = 4.0 J. (a) What is the magnitude of $\stackrel{\to }{F}$? (b) What is the value of k?

Figure 7-36 Problem 30.