The position versus time for a certain object moving along the x-axis is shown. The object’s initial position is −2 m. Find the instantaneous velocity at 1s. http://img23.imageshack.us/img23/5285/phy1w.jpg [Broken] Using points (0,-2) and (2,7) I found the equation of the line to be =7/2x-2. Since this is a straight line I thought the tangent line would have the same slope. So, at 1s the instantaneous velocity would be 7/2, but this is not the correct answer. Where am I going wrong?