To solve this problem we require the concept of Forces given by Newton in his second law. For the particular case where the acceleration is 0 and when there is a change of acceleration.
A) For the first case where the speed is constant we have to
[tex]F = mg[/tex]
Here,
[tex]a=0m/s^2[/tex]
Then,
[tex]F= mg[/tex]
[tex]40N = m (9.8)[/tex]
[tex]m = 4.077kg[/tex]
B) Here we have an acceleration of [tex]2.57m / s ^ 2[/tex]. When there is acceleration it is considered that the sum of forces is dynamic, for that reason when performing the summation, we have
[tex]\sum F = ma[/tex]
[tex]F-mg = ma[/tex]
[tex]T = m(a+g)[/tex]
[tex]40= m(9.8+2.57)[/tex]
[tex]m = 3.23kG[/tex]
Therefore the heaviest fish that can be pulled up vertically is 3.23KG when there is acceleration but 4.077kg with constant velocity