일반물리학 1 — Kinetic Energy and Work: Problem 30

30 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 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. 7-29. The scale of the vertical axis is set by Ks = 6.0 J. (a) What is the magnitude of F? (b) What is the value of k?