Buoyancy of salted water

Classical Mechanics Level 1

In science, buoyancy is an upward force exerted by a fluid that opposes the weight of an immersed object. The above left shows a can of Pepsi sunken in pure water, and the above right shows the same can of Pepsi floating in salted water. Which of the following statements is correct?

a) The buoyancy force upon the right Pepsi can is greater than the buoyancy force upon the left Pepsi can.

b) The gravity force upon the left Pepsi can is greater than the gravity force upon the right Pepsi can.

c) The weights of fluid pushed by the left Pepsi and the right Pepsi cans are the same.

a) only b) only c) only a), b) and c)

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Lakshan Dumpa by Lakshan Dumpa , 24, India

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3 solutions

Lalita Verma
Mar 4, 2014

c)=weight of both fluid are not same because salt water has high viscosity.so it has high density. so its mass also high but pure water has low mass.so weight of salt water is high b)=gravity force always same for every object a)=if weight of salt water is high then buoyancy force also high . so a) is correct

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Vinayak Rastogi
Mar 1, 2014

we can very well see that only option a is correct , because as option b says that gravity on both if them is different which is actually not true because gravity has a constant value for a given height which implies that the difference is there in the force of buoyancy which is obviously greater in the second one ( in which the glass is floating ) which proves option a - correct and option c is obviously wrong because the force of buoyancy on both the cans are varying because of the different masses of water.......... :) quite a simple question but a conceptual one ...... nice !!!!

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I think option a is wrong, the buoyancy in left is the same with buoyancy in right since both can (object) displaced the same volume of water. with the same volume and same density means the same weight of water displaced. therefore same buoyancy on both. the left can sink simply because it is less dense than water. maybe right can is empty. thanks

Stalin Garcia - 7 years, 3 months ago

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Actually they don't displace the same weight of the water as the density of salt water is more than that of pure water so the one on the right displaces a greater weight of water and thus experiences a greater upthrust.

Parth Dhar - 7 years, 3 months ago

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Rightly said !!

Vinayak Rastogi - 7 years, 3 months ago

i agree

Shaista Rehman - 7 years, 3 months ago

I actually meant statement a not option..... Just got a bit confused

Vinayak Rastogi - 7 years, 3 months ago

the density of salted water is greater than simple water that why it float

Lokpal Negi - 7 years, 3 months ago
Shivangi Sharma
Mar 2, 2014

Option B is wrong as the gravitational force is always the same. It never changes. Clearly, option C is wrong as weight of both the fluid is different.

1 Helpful 0 Interesting 0 Brilliant 0 Confused

By fluid do mean the contents of the can or the fluid which surrounds the can?

Çmïr Dârth'ánnìa - 7 years ago

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