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: Option 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