1997 General Studies, all questions
UPSC Prelims 1997 · General Studies
Question 144: Science and Technology
A girl is swinging on a swing in sitting position. When the same girl stands up, the period of swing will
abe shorter
bbe longer
cdepend on the height of the girl
dnot change
AnswerThe answer is (a).
A girl who stands up on a swing raises her centre of mass, which shortens the effective length of the pendulum. The period of a pendulum is 2π√(L/g), so a shorter length gives a shorter period and the swing goes faster. Mass does not enter the formula, which is why the girl's weight makes no difference.
Why each option is right or wrong
- (a) Right: standing shortens the effective length, so the period is shorter.
- (b) A longer period would need a longer effective length, and standing shortens it.
- (c) The period depends on the effective length, not on the girl's height as such.
- (d) The period depends on length, which changes, so it does change.
Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 1997, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.