For the three-mass configuration in an elevator at rest, what is the force Fspring,top that the top spring exerts on the Learning Goal: use Newton's second law to analyze a top mass? hanging, accelerated spring-mass system. Macmillan Learning 33.0 In the first configuration, a single mass m1 = 3.30 kg hangs Fspring, top= N from a massless spring in a motionless elevator. The spring Incorrect extends a length y = 13.0 cm from its unstretched length. (Scroll down for the second configuration.)