What is the term for the backward force experienced by firefighters when water exits a nozzle?

• A. Nozzle reaction
• B. Backlash
• C. Hydraulic backpressure
• D. Counterflow

Answer: (A)

When water is expelled from a nozzle, a backward push on the nozzle occurs. This is nozzle reaction, the direct result of Newton's third law: as water is accelerated out of the nozzle, the nozzle and hose experience an equal and opposite force. The stronger the flow and the higher the exit velocity, the larger the reaction force. That’s why firefighters must brace and sometimes adjust nozzle type and pressure to manage recoil. The other terms refer to different ideas—backlash is a mechanical play in gears, hydraulic backpressure is pressure built up in a line, and counterflow means flow in the opposite direction—so they don’t describe the backward thrust felt at the nozzle like nozzle reaction does.