During this time interval, the unbalanced forces are the downward forces which include drag force and weight of the object.
The net force on the object is obtained by summing all the forces acting on the object.
Let the upward force = positive
Let the downward force = negative
Net force = (50 N + 40 N) - (20 N + 40 N)
Net force = 90 N - 60 N = 30 N
Thus, during this time interval, the unbalanced forces are the downward forces which include drag force and weight of the object.
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