- #26

gneill

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For part (b), on page one of your upload images, you wrote:

Note the indicated line. Since block A is stationary in the chosen frame of reference (the elevator), the sum of the forces acting on it must be zero.

The same applies for part (e) where you are looking for the normal force on the elevator floor: Choosing the elevator as the frame of reference, block A is stationary on the floor, so that the sum of forces must be zero in that frame of reference. You can write the same equation using your effective value of "g".