The volume of a sealed packet is 1 litre and its mass is 800 g. The packet is first put inside water with density 1 g cm⁻³ and then in another liquid B with density 1.5 g cm⁻³. Then which one of the following statements holds true?
- A.The packet will float in both water and liquid B.
- B.The packet will sink in both water and liquid B.
- C.The packet will sink in water but will float in liquid B.
- D.The packet will float in water and sink in liquid B.
Correct answer
Explanation
The correct answer is A, The packet will float in both water and liquid B. The packet’s density is 800 g divided by 1,000 cm³, which is 0.8 g/cm³, less than the density of both liquids.
An object floats in a liquid when its average density is lower than the liquid’s density, and sinks when it is higher. This follows from Archimedes’ principle: a body in a fluid is pushed up by a force equal to the weight of the fluid it displaces. Fully under water, the packet would displace 1,000 g of water, more than its own 800 g, so it rises and floats with about 80% of its volume submerged. In liquid B, with density 1.5 g/cm³, it floats even higher, with only about 53% submerged. A denser liquid always gives a larger buoyant force for the same volume.
B is wrong because the packet is lighter than an equal volume of either liquid, so it cannot sink. C is wrong because it floats in water as well. D is wrong because a denser liquid pushes up even harder, so a packet that floats in water must float in liquid B.
Exam tip: density of object below density of liquid = floats; fraction submerged = object density divided by liquid density.
Practice Questions
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- A.higher concentration to its lower concentration through a cell wall.
- B.lower concentration to its higher concentration through a fully permeable membrane.
- C.higher concentration to its lower concentration through a fully permeable membrane.
- D.higher concentration to its lower concentration through a semi-permeable membrane.
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- B.paramagnetic property
- C.ferromagnetic property
- D.electromagnetic property
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Read the full explanation →The chemical properties of an element depend upon
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- B.the mass number of the element
- C.the total number of neutrons in the element
- D.the number of electrons in the outermost shell of the element
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- A.Free ribosomes
- B.Mitochondria
- C.Nucleolus
- D.Cell wall
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Read the full explanation →A student was doing an experiment on increasing the cell division among plants. She asked her supervisor to suggest the specific plant hormone for the same. Had you been her supervisor, which plant hormone would you suggest?
- A.Abscisic acid
- B.Gibberellins
- C.Cytokinin
- D.Auxin
Show answer
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Read the full explanation →