Buoyancy & Buoyant Force Video Lessons

Concept

# Problem: A flask of water rests on a scale that reads 100N. Then, a small block of unknown material is held completely submerged in the water. The block does not touch any part of the flask, and the person holding the block will not tell you whether the block is being pulled up (keeping it from falling further) or pushed down (keeping it from bobbing back up).The experiment is repeated with the six different blocks listed below. In each case, the blocks are held completely submerged in the water.Mass (g)Volume (cm3)A10050B100200C20050D50100E200100F40050Rank these blocks on the basis of the scale reading when the blocks are completely submerged.Rank from largest to smallest. To rank items as equivalent, overlap them.

###### FREE Expert Solution

Buoyant force, FB:

$\overline{){{\mathbf{F}}}_{{\mathbf{B}}}{\mathbf{=}}{\mathbf{\rho }}{\mathbf{V}}{\mathbf{g}}}$

Where ρ is the density of the fluid, V is the volume of the fluid displaced, and g is the gravitational acceleration.

The scale reading increases by an amount equal to the upthrust force exerted on the block

The upthrust force is directly proportional to the volume of the object. It is independent of the mass of the object and density of the object.

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###### Problem Details

A flask of water rests on a scale that reads 100N. Then, a small block of unknown material is held completely submerged in the water. The block does not touch any part of the flask, and the person holding the block will not tell you whether the block is being pulled up (keeping it from falling further) or pushed down (keeping it from bobbing back up).

The experiment is repeated with the six different blocks listed below. In each case, the blocks are held completely submerged in the water.

 Mass (g) Volume (cm3) A 100 50 B 100 200 C 200 50 D 50 100 E 200 100 F 400 50

Rank these blocks on the basis of the scale reading when the blocks are completely submerged.

Rank from largest to smallest. To rank items as equivalent, overlap them.

What scientific concept do you need to know in order to solve this problem?

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