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Question
A solid of R.D. = 2.5 is found to weigh 0.120 kgf in water. Find the wt. of solid in air.
Solution
Relative density of solid = R.D. = 2.5
Weight of solid in water = W’ = 0.120 kgf
Weight of solid in air = W = ?
R.D. = `"Weight of solid in air"/("wt. of solid in air"-"wt. of solid in water")`
R.D. = `"W"/("W" - "W"')`
2.5 = `"W"/("W" - 0.120)`
2.5 W - 2.5 × 0.120 = W
2.5 W - 0.3 = W
2.5 W - W = 0.3
1.5 W = 0.3
W = `0.3/1.5` = 0.20 kgf
So, weight of solid in air = 0.20 kgf
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