Physics' Concept - 1

Classical Mechanics Level 3

A bottle is cut and a ping-pong ball is placed near its mouth as shown in the figure.Now a strong person blows hard from the mouth of bottle in the direction of the arrow shown in order to lift the ball .Will the ball get lifted?

Possible , if the mouth of the cut bottle is made wider. Always Possible , if the mouth of the cut bottle is made longer. It depends on the force that the blower exerts on the ball. Only if the ball size is increased. Never

Nihar Mahajan by Nihar Mahajan , 20, India

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1 solution

Nihar Mahajan
May 16, 2015

Since the person is blowing air , the air molecules are in motion.Thus by Bernoulli's principle , a low pressure area will be created below the ball and the pressure above the ball is comparatively high.Hence the ball will always tend to move down however hard the person blows.For more explanation click here

7 Helpful 0 Interesting 0 Brilliant 0 Confused

Yes It is .. But It is an approximate explanation . Since Bernoulli is applicable for same fluids , Here when you blow's air from your mouth , then the fluid below the ball and above the ball are different.

So yes it can be accepted as an approximate explanation .

There are many such examples where we un-necessarily explain by Bernoulli , Like as : Famous example , when we blow air from our mouth in bottom of an light paper then it will rise downward , instead moving upward . Generally some teachers explain that it is because of Bernoulli , velocity increase on bottom and hence pressure decreases , So it moves downwards . But this is not correct explanation . Since flow fluids on both sides are different . Plus when we blow air then pressure should remain as Patm by logic .

You may search it on Wikipedia , Bernoulli principle application , they pointed out same thing . It is interesting . Search it !

Nishu sharma - 6 years ago

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Thanks for your note ☺

Nihar Mahajan - 6 years ago

I had seen a similar experiment in discovery science, the program me was "head rush". It really defies logic!

T H U M B S U P ! \huge THUMBS\quad UP!

Sravanth C. - 6 years ago

In the video, the ball didn't move vertically but executed some rotational motion. Due to dynamic lift?

Dwija Parikh - 5 years, 11 months ago

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