I have a question involving the spring costant: A 2-kg block is attached to a horizontal ideal spring with a spring constant of 200N/m. When the spring has its equilibrium length the block is given a speed of 5 m/s. What is the maximum elongation of the spring? To my understanding when the spring is at its equilibrium length, isn't there no force acting on the spring. So how would you work around it to solve for length. I would appreciate help in how to go about solving the problem. Thank you.