An iron nail sinks in water whereas an iron ship floats. Which of the following statements is correct in this regard? 1. Average density of ship is greater than that of the water 2. Average density of iron nail is greater than that of the water 3. Average density of the ship is less than that of the water 4. Average density of the ship is equal to that of the water Select the correct answer using the code given below:
- A.1 and 2
- B.2 and 3
- C.2 and 4
- D.1 and 4
Correct answer
Explanation
The correct answer is B, 2 and 3. An object floats when its average density is less than that of the liquid and sinks when it is greater. A solid iron nail has the density of iron, about 7.8 g per cubic centimetre, nearly eight times that of water, so the buoyant force on it is less than its weight and it sinks; statement 2 is correct. A ship is also made of iron or steel, but it is shaped as a hollow hull filled largely with air. Its total mass is spread over a very large volume, so its average density is less than that of water. It sinks only until it has displaced water equal to its own weight, as Archimedes' principle says, and then floats; statement 3 is correct. Option A is wrong because if the ship's average density were greater than water, it would sink. Option C is wrong because equal density would leave the ship just suspended, fully submerged, not floating with a part above water. Option D is wrong because both its statements about the ship are false. Exam tip: average density below that of the liquid means it floats.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
Read the full explanation →Which one of the following statements is correct?
- A.Urea is produced in liver.
- B.Urea is produced in blood.
- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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Read the full explanation →Which one of the following is the correct sequence of passage of light in a compound microscope?
- A.Condenser-Objective lens-Eyepiece-Body tube
- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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Light passes through the condenser to the specimen, is picked up by the objective lens, travels up the body tube and reaches the eye through the eyepiece.
Read the full explanation →Which one of the following statements regarding haemoglobin is correct?
- A.Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
- B.Haemoglobin of RBC can carry both oxygen and carbon dioxide.
- C.Haemoglobin of RBC can carry only carbon dioxide.
- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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It binds oxygen at its iron-containing haem groups and carries some carbon dioxide on its protein chains. Each haemoglobin molecule has four polypeptide chains and four haem groups, and each haem iron can hold one oxygen molecule, forming oxyhaemoglobin in the lungs.
Read the full explanation →Which one of the following statements regarding histone proteins is correct?
- A.Histones are proteins that are present in mitochondrial membrane.
- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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They are the proteins around which DNA winds to form chromatin in the nucleus of eukaryotic cells. Histones are small basic proteins, rich in the positively charged amino acids lysine and arginine, which attract the negatively charged phosphate groups of DNA.
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