question_answer

A liquid of density \[\rho \] is coming out of a hose pipe of radius a with horizontal speed v and hits a mesh. 50% of the liquid passes through the mesh unaffected. 25% looses all of its momentum and 25% comes back with the same speed. The resultant pressure on the mesh will be-           [JEE Main 11-Jan-2019 Morning]

A) \[\rho {{v}^{2}}\]

B) \[\frac{1}{4}\rho {{v}^{2}}\]

C) \[\frac{3}{4}\rho {{v}^{2}}\]

D) \[\frac{1}{2}\rho {{v}^{2}}\]

Correct Answer: C

Solution :

[c] The momentum per second carried by liquid per second is

[A is area of cross section of pipe]

The force exerted due to reflected back molecules

So, the resultant pressure is