An object weighs 30N in air and 21N in water. The weight of the object when completely immersed in a liquid of relative density 1.4 is
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Correct Answer: Option B
Explanation:
Weight of water displaced = upthrust = 30 - 21 = 9N
 Mass of water displaced = \(\frac{9}{10}\) = 0.9kg
 Volume of object = 9 × 10\(^{-4}\)m\(^3\)
 = (9 × 10\(^{-4}\)) (1.4 ×103)
 = 1.26kg = 12N
 30 - 12.6 = 17.4N
Weight of water displaced = upthrust = 30 - 21 = 9N
 Mass of water displaced = \(\frac{9}{10}\) = 0.9kg
 Volume of object = 9 × 10\(^{-4}\)m\(^3\)
 = (9 × 10\(^{-4}\)) (1.4 ×103)
 = 1.26kg = 12N
 30 - 12.6 = 17.4N