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
A
25.2N
B
17.4N
C
12.6N
D
9.0N
Verified Correct Answer: B.
Physical Principles & Numerical Solution
Weight of water displaced = upthrust = 30 - 21 = 9N
Mass of water displaced = \(\frac{9}{10}\) = 0.9kg
Volume of object = 9 \times 10\(^{-4}\)m\(^3\)
= (9 \times 10\(^{-4}\)) (1.4 \times103)
= 1.26kg = 12N
30 - 12.6 = 17.4N
Source: Myschool Past Questions Archive (Record #47743)