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A wide rectangular tank has two holes, one on each of two opposite vertical walls. Each hole has cross-sectional area 0.01 m², and the vertical separation between the two holes is 1 m. The tank is filled with water. Find the net horizontal reaction force on the tank as water streams out of both holes. (Density of water = 1000 kg/m³, take g = 10 m/s².)
- 100
- 200
- 300
- 400
Correct answer: 200
Solution
Thrust from a jet = rho*A*v² = rho*A*(2gh). The two holes are on opposite walls so their reactions oppose. Net force = rho*A*2g*(h_lower - h_upper) = rho*A*2g*(vertical separation) = 1000*0.01*2*10*1 = 200 N.
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