A 8.4 kg mass is attached to a light cord that passes over a massless, frictionless pulley. The other end of the cord is attached to a 3.7 kg mass. Use conservation of energy to determine the ?nal speed of the ?rst mass after it has fallen (starting from rest) 7.6 m .The acceleration of gravity is 9.8 m/s 2. Answer in units of m/s