Instructions: A block sitting on a frictionless table is attached to a spring. Drag the sliders to set the initial position and velocity of the block, and then press start to watch the animation of its motion. On the right you’ll see the plot of the potential energy curve $U = \frac{1}{2} k x^2$, and how the potential energy of the system changes as the block moves. The dashed horizontal line represents the total energy $E = \frac{1}{2}mv^2 + U$ of the block. Press reset to stop the animation, and drag the sliders again to choose different initial conditions.