Question

A pressure-pump has a horizontal tube of cross-sectional area 10 cm² for the outflow of water at a speed of 20 m/s. The force exerted on the vertical wall just in front of the tube which stops water horizontally flowing out of the tube, is: 

[given : density of water = 1000 kg/m³] 

(A) 300 N 

(B) 500 N 

(C) 250 N 

(D) 400 N

Answer 1

Correct option is (D) 400 N

F = Pa\(\nu\)² = 10³ x 10 x 10^-4 x 20 x 20

F = 400

Comments

Sir from where 10(to the power -4) came?

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when convert cm^2 to m^2 then we multiply 10^-4.

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to convert 1 cm^2 to 1 m^2, 1m = 100cm, so 1cm = 1/100 or 10^-2 m                                                                                           therefore 1cm^2 = (10^-2)^2 = 10^-4 m2