A ping pong ball is placed in a funnel as shown in the \"PingPongFunnel\" figure

Question

A ping pong ball is placed in a funnel as shown in the "PingPongFunnel" figure. It is noted that it is not possible to move the ball out of the funnel by blowing air in from the small end. This is true for both orientations of the setup shown. A fluid dynamicist can explain this phenomena as Bernoullis Equation indicates a depressed pressure region in the narrow gap beween the ball and the funnel wal Viscous effects along the funnel wall and around the surface of the ball interact to produce a retaining force. The ball likely spins and that produces lift. Non-Newtonian fluid effects dominate

Explanation / Answer

As per Bernoulis priniciple pressure is directily proportional to the speed of the fluid, from the equation of continiuity speed is inversily proportional to the area

from the figure , the area of funnel is small so speed of the fluid is large, then the pressure acting on the ball is also large in the narrow region

so option (a) is wrong

Viscous effects along the funnel wall and around the surface of the ball interact to produce a retaining force due to this reason ball does not come out of the funnel.

option (B) is correct

ball does not sprin so option (c) is wrong

ball shape does not change so  Non-Newtonian fluid effects does not dominate

so option (d) is wrong

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