A single mass (m 1 = 2.8 kg) hangs from a spring in a motionless elevator. The s

Question

A single mass (m1 = 2.8 kg) hangs from a spring in a motionless elevator.  The spring constant is k = 310 N/m.

Now, three masses (m1 = 2.8 kg, m2 = 8.4 kg and m3 = 5.6) hang from three identical springs in a motionless elevator.   The springs all have the same spring constant given above.

the elevator is moving downward with a velocity of v = -2 m/s but accelerating upward at an acceleration of a = 4.5 m/s2.   (Note: an upward acceleration when the elevator is moving down means the elevator is slowing down.)

Finally, the elevator is moving downward with a velocity of v = -3.8 m/s but accelerating downward at an acceleration  of a = -2.2 m/s2.

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

Please show steps

Explanation / Answer

As far as I understood the question,if all masses are attached to roof of the elevator and considering only final acceleration as acceleration of elevator

Net force on middle mass=m(a-g)

                =8.4*(-2.2-9.8)

                =-100.8 N

i.e,100.8 N force acting downwards

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