Practice question
Question
A spray tube (7cm2) has 35 holes of diameter 0.8mm. If the flow speed is 3.0m/min, what is the ejection speed?
Explanation
A1v1 = A2v2, v1 = 3.0m/min = 0.05m/s, A1 = 7×10−4m2. Hole area: Ah = π(0.4×10−3)2, total A2 = 35×π×1.6×10−7≈1.759×10−5m2. v2 = 7×10−4×0.051.759×10−5≈1.99m/s. As per NCERT, applying relevant law/formula with correct units and sign convention leads to 2.0 m/s. This satisfies dimensional consistency and physical conditions given, so option B is scientifically correct.