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Question
A body of volume 100 cm3 weighs 1 kgf in air. Find:
- Its weight in water and
- Its relative density.
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Solution
Volume of body = 100 cm3
Weight in air, W1 = 1 kgf = 1000 gf
Mass of body = 1 kg = 1000 g
R.D. of solid = 10
R.D. of water = 1
(i) Let W2 be the weight of the body in water.
R.D. of body = `W_1/(W_1 - W_2) xx "R.D. of water"`
or , 10 = `1000/((1000 - W_2)) xx 1`
or, 10(1000 - W2) = 1000
or, 1000 - W2 = 100
or, W2 = 900 gf = 0.9 kgf
(ii) R.D. of body = Density in C.G.S. (without unit)
or, R.D. = `"Mass"/"Volume" = 1000/100 = 10`
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