Final answer:
The magnitude of force required to move a plate in a fluid depends on velocity, area, distance between plates, and viscosity. The force in the context of a magnetic field is calculated differently. To determine forces acting on a plank, the moments about a point are assessed because the system is in static equilibrium.
Step-by-step explanation:
The student is inquiring about the force F required to maintain constant velocity of a plate moving through a fluid, a concept rooted in fluid mechanics within Physics. The four factors affecting this force—velocity (v), area (A), distance between plates (L), and viscosity (n)—are described. To find the magnitude of the force, we would typically need the particular equation combining these factors. However, in the absence of the exact formula, a general approach is to combine the proportionalities (direct and inverse) to the force F. If the specific fluid flow context—like laminar flow between parallel plates—is known, the equation is usually derived from the Navier-Stokes equations and is of the form:
F = (n * A * v) / L
where n is the viscosity, A is the area, v is the velocity, and L is the separation distance. In the scenario involving the magnetic field, the equation given (F = quBsin(Θ)) is used to calculate the force on a charge moving in a magnetic field, which is a different context from fluid mechanics. Lastly, in the example with the person carrying a plank, to find the magnitudes of the forces F1 and F2, moments about a point would be set equal because the plank is in static equilibrium.