A mass m₁ on a horizontal shelf is attached by a thin string that passes over a frictionless peg to a 2.5- kg mass m₂ that hangs over the side of the shelf 1.5 m above the ground (Figure). The system is released from rest at t = 0 and the 2.5-kg mass strikes the ground at t = 0.82 s. The system is now placed in its initial position and a 1.2-kg mass is placed on top of the block of mass m₁. Released from rest, the 2.5-kg mass now strikes the ground 1.3 s later. Determine the mass m₁ and the coefficient of kinetic friction between m₁ and the shelf.

m2