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In a spray gun, a piston of radius 20 mm pushes air out through a nozzle of radius 1 mm. If the piston advances at a speed of 5 mm/s, find the speed at which air emerges from the nozzle.
- 0.1 m/s
- 1 m/s
- 2 m/s
- 8 m/s
Correct answer: 2 m/s
Solution
By continuity, A1*v1 = A2*v2, so v2 = v1*(r1/r2)² = 5 mm/s * (20/1)² = 5 * 400 = 2000 mm/s = 2 m/s.
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