Final answer:
Nozzles operating at pressures less than 100 psi are characterized by producing smaller droplet sizes due to the Bernoulli effect, where increased velocity compensates for lower pressure.
Step-by-step explanation:
Among the options provided for the characteristics of nozzles operating at pressures less than 100 psi (700 kPa), the most accurate characteristic is that they would produce droplets of smaller size. This is because a lower pressure nozzle tends to mist the water more, breaking it into finer particles. Nozzles designed to work at lower pressures won't necessarily have more nozzle reaction because nozzle reaction is more correlated with the flow rate and velocity of the water. They also are not necessarily associated with lower-density fog patterns nor do they produce fire streams with greater velocity compared to higher pressure nozzles. Generally, higher pressure results in a higher velocity of the water exiting the nozzle.
The Bernoulli effect is key to understanding how these nozzles can still be effective even with a lower pressure. According to the Bernoulli principle, as the velocity of a fluid increases, the pressure within the fluid decreases. Thus, in the scenario where water moves uphill and through a converging nozzle, the water's kinetic energy increases which compensates for the lower pressure, allowing it to still exert a significant force upon whatever it strikes. This is why water can exit the nozzle against the opposing atmospheric pressure; the increased kinetic energy from the higher velocity compensates for the lower pressure.