A copper cube weighs 0.25 N in air, 0.17N when completely immersed in paraffin oil and 0.15 N when completely immersed in water.The ratio of upthrust in oil to upthrust in water is
A. 3 : 5 B. 4 : 5 C. 7 : 10 D. 13 : 10
Correct Answer: B
Explanation
Wt. in air = 0.25 N Wt.in water = 0.15 N therefore lost in wt. in water = Upthrust in water = 0.25 - 0.15 = 0.10 N. Wt. in paraffin oil = 0.17 N. .. loss in wt.in oil = upthrust in the oil Ratio upthrust in oil to upthrust in water = 0.18/0.10 = 8/10 = 4/5 Or 4 : 5
