2004 General Studies, all questions
UPSC Prelims 2004 · General Studies
Question 128: Science and Technology
A weightless rubber balloon is filled with 200 cc of water. Its weight in water is equal to
a9.85 N
b9.8/10 N
c9.8/2 N
dzero
AnswerThe answer is (d).
The balloon is weightless, so its weight in water comes from the 200 cc of water inside it, about 1.96 N, less the buoyant force on it. The buoyant force equals the weight of the water displaced, the same 200 cc, so also about 1.96 N upward. The two cancel, and the weight in water is zero.
Why each option is right or wrong
- (a) 9.85 N would be about a litre of water.
- (b) 0.98 N is not the water's weight.
- (c) 4.9 N is not the water's weight.
- (d) Correct: weight and buoyancy cancel, giving zero.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2004, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.