To solve this problem, we can use Hooke's Law which states that the force exerted by a spring is directly proportional to its displacement from equilibrium. Mathematically, this can be expressed as:
F = -kx
where F is the force exerted by the spring, x is the displacement of the spring from equilibrium, and k is the spring constant.
In this problem, we know that the spring is stretched by 0.15 m and exerts a force of 3.5 N. We also know that the spring constant is 23.3 N/m.
Using Hooke's Law, we can find the mass of the fish as follows:
F = -kx
3.5 N = -(23.3 N/m) * 0.15 m - mg
where g is the acceleration due to gravity (9.8 m/s^2) and m is the mass of the fish.
Solving for m, we get:
m = (-(23.3 N/m) * 0.15 m - 3.5 N) / 9.8 m/s^2
m = 0.0676 kg
Therefore, the mass of the fish is 0.0676 kg.