A single mass (m1 = 4.4 kg) hangs from a spring in a motionless elevator. The spring constant is k = 275 N/m.

Now, three masses (m1 = 4.4 kg, m2 = 13.2 kg and m3 = 8.8) hang from three identical springs in a motionless elevator. The springs all have the same spring constant given above.

Finally, the elevator is moving downward with a velocity of v = - 2.1 m/s but accelerating downward at an acceleration of a = - 2.1 m/s2.

What is the magnitude of the net force on the middle mass?