Certified Safety Professional Practice Exam

The velocity of fluid flowing through a hole in a tank, as described by Torricelli's Law, is primarily determined by the height of the fluid above the hole. This is because the potential energy of the fluid due to its elevation is converted into kinetic energy as the fluid exits the hole. According to Torricelli's Law, the speed (velocity) of the efflux is proportional to the square root of the height of the fluid column above the hole.

When the height of the fluid increases, there is more gravitational potential energy available to convert into kinetic energy, resulting in higher fluid velocity as it exits. Conversely, if the height decreases, the pressure exerted by the fluid also reduces, leading to a decrease in velocity.

While factors like viscosity and pressure differences do play roles in fluid dynamics, they are not the primary determinants of velocity according to Torricelli's formulation. Thermal energy is also unrelated to the phenomenon described by this law. Thus, the height of the fluid above the hole directly correlates to the velocity at which the fluid exits, making it the correct choice.