A 2-kilogram block is attached horizontally to a spring on a frictionless surface, as shown above. The spring has a spring constant of 200 newtons per meter and negligible mass. The string is compressed 15 cm to the left. (A) Determine the speed of the block at the instant it goes through its equilibrium position.
(B)Determine the period of the block.
(C)Determine the frequency of the block.
(D) Where is the kinetic energy of the block at a maximum? Explain.

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.