1.

A particle at the end of a spring executes SHM with a period t_(1), while corresponding period for another spring is t_(2). If the period of oscillation when the two springs are connected in series is T, then prove that, t_(1)^(2)+t_(2)^(2)=T^(2).

Answer»

Solution :LET the mass of the particle be m and SPRING constants of the SPRINGS be `k_(1)andk_(2)`.
In first case,
`t_(1)=2pisqrt(m/k_(1))or,t_(1)^(2)=4pi^(2)(m/k_(1))""...(1)`
In second case,
`t_(2)=2pisqrt(m/k_(2))or,t_(2)^(2)=4pi^(2)(m/k_(2))""...(2)`
In series the equivalent spring CONSTANT is k,
Then, `1/k=1/k_(1)+1/k_(2)or,k=(k_(1)k_(2))/(k_(1)+k_(2))`
`therefore` Time PERIOD of the combination,
`T=2pisqrt(m/k)=2pisqrt((m(k_(1)+k_(2)))/(k_(1)k_(2)))`
or, `T^(2)=(4pi^(2)m(k_(1)+k_(2)))/(k_(1)k_(2))`
adding (1) and (2) we get,
`t_(1)^(2)+t_(2)^(2)=4pi^(2)(m/k_(1)+m/k_(2))=4pi^(2)m(1/k_(1)+1/k_(2))`
`=4pi^(2)m((k_(1)+k_(2))/(k_(1)k_(2)))`
`therefore" "t_(1)^(2)+t_(2)^(2)=T^(2)` (Proved).


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