Final answer:
With the information provided, it's not feasible to calculate Ysabela's average acceleration during the freestyle race, as the final velocity at the moment she reaches the wall is not given and cannot be assumed to be 0 m/s or constant.
Step-by-step explanation:
To determine Ysabela's average acceleration during a 25 m freestyle race, we can use the kinematic equation for constant acceleration, which states that the final velocity squared equals the initial velocity squared plus two times the acceleration times the distance (v^2 = u^2 + 2ad). Assuming Ysabela starts from rest, we have the initial velocity (u) as 0 m/s, and the distance (d) is 25 m. Now, it's also given that it takes her 20 seconds to reach the other wall, but we need her final velocity first for this equation. We can get the final velocity using the equation for velocity with constant acceleration, which is v = u + at.
Since she's reached the wall, her velocity will be 0 m/s at the moment of touching the wall (ignoring practical considerations like turning etc.). However, this does not help us with the equation as it implies the acceleration would be zero which would contradict the question's premise. Instead, we use the assumption that she is at her maximum velocity when she touches the wall, and the time given is for the total swim. As it's not possible to calculate average acceleration without the final velocity and with the information provided being insufficient, the problem as stated cannot be accurately solved. The standard approach to a question like this would be to assume a return to zero velocity at the wall or a constant speed during the swim but both do not reflect the average acceleration over the distance.