A firefighter estimates how far a horizontal water jet from a hose will travel before…
PHYSICS · Single correct · CBSE · Physics · Mechanical Properties of Fluids · Mechanical Properties of Fluids
Problem
A firefighter estimates how far a horizontal water jet from a hose will travel before hitting the ground by treating the water as an ideal fluid leaving the nozzle at speed v0. In reality, the jet lands significantly closer than predicted. Which combination of factors most plausibly explains the overestimate?
(a) Compressibility of water under the relatively low pressure in the hose makes the fluid expand, so it leaves at a lower density and therefore carries less momentum.
(b) Energy losses due to viscosity in the hose reduce v0, and the water experiences appreciable air drag in flight, both of which shorten the range.
(c) Because water is denser than air, the jet "falls" faster than a projectile of negligible mass, so it reaches the ground sooner than predicted.
(d) Surface tension between the water and the surrounding air pulls backward on the jet, removing most of its horizontal motion immediately after it leaves the nozzle.