fluids

I am drinking a glass of lassi or juice. I insert a straw (perpendicularly) inside it. Let's say that for a certain value of the thickness(density) of the juice, the straw stands still straight. what is the minimum density of the juice required to keep the straw still and what relation does it have with the density of the straw?

1 Answers

111
Rajiv Agarwal ·

Let the:
Inner radius of the straw be "a"
Outer radius be "b"
Height be "l"
Height immerse perpendicularly in the liquid be "x"
Density of the material of the straw be "c"
Density of the liquid be "d"

As the straw is in equilibrium,
mg = buoyant force
or, π(b2-a2)*l*c*g = π(b2-a2)*x*d*g
or, l/x = d/c

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