Question

A pendulum of length 36 cm has a time period of 1.2 s. Find the time period of another pendulum, whose length is 81 cm.

Answer 1

l₁ = 36 cm, T₁ = 1.2 s

l₂ = 81 cm, T₂ = ?

`"T"_1/"T"_2=sqrt("l"_1/"l"_2)`

`1.2/"T"_2=sqrt(36/81)`

`1.2/"T"_2=6/9`

T₂ = `(9xx1.2)/6` = 9 × 0.2 = 1.8 s