Two boxes, A and B, are connected to each end of a light vertical rope, as shown in the following figure. A constant upward force 820 N is applied to box A. Starting from rest, box B descends 12.8 m in 4.30 s. The tension in the rope connecting the two boxes is 40.0 N (Figure 1)
Figure
Part A
What is the mass of box B?
Express your answer with the appropriate units.
$m_B =$
Part B
What is the mass of box A?
Express your answer with the appropriate units.
$m_A =$