An ideal spring is hung vertically from the ceiling. When a 2.00-kg mass hangs at rest from it the spring is extended 19.6 cm from its relaxed length. It is then attached to a 1.00-kg mass on a frictionless horizontal surface and is used to compress the spring for 5.00 cm. The block is then let go. (a) What is the spring constant k? (b) What is the speed of the spring when it is being stretched for 1.00 cm during the motion?