Final answer:
In a no wake zone, the question's provided information about boat velocities in relation to water currents and drag coefficients does not directly answer the maximum speed of vessels. However, it illustrates the physics concept of vector addition to determine the boat's velocity with respect to the Earth in a scenario with a river current.
Step-by-step explanation:
In the context of a no wake zone, the question seems to be unrelated to the provided information about boat speeds in currents and drag coefficients. However, addressing the physics concept related to the information given, we can analyze the situation of a boat moving across a river current. When a boat tries to cross a river, its actual speed with respect to the Earth is the result of the combination of its own speed across the water and the speed of the river current.
Considering the examples provided, if a boat heads north in still water at 4.5 m/s and the river runs east at 3.0 m/s, the boat's velocity with respect to Earth can be found by using vector addition. Similarly, if a boat attempts to travel straight across a river at 0.75 m/s and the river's current is 1.20 m/s to the right, the boat's resultant velocity relative to the Earth would again require vector analysis.