The period when the length is 49 in. is 3.5 seconds. So, the correct answer is C:
![\[ \text{Period} = 3.5 \, \text{sec} \]](https://img.qammunity.org/2024/formulas/physics/high-school/a9fo4r2zym5pi2mg5diur3jq45udrhsgi5.png)
The relationship between the period
of a pendulum and its length
is given as:
![\[ p \propto √(l) \]](https://img.qammunity.org/2024/formulas/physics/high-school/ju3em38jxzc4vcnpvzfleuirsbs1kvl8cz.png)
This can be written as an equation with a constant of proportionality
:
![\[ p = k √(l) \]](https://img.qammunity.org/2024/formulas/physics/high-school/rvft5ho458hq6sja98l9ypkwbk1iegbpzw.png)
To find
, use the initial values where
is 2.5 sec. when
is 25 in.:
![\[ 2.5 = k √(25) \]](https://img.qammunity.org/2024/formulas/physics/high-school/bhzipfqkjgoxvsugsxu3wg5fmznphsm2sa.png)
Solve for
:
![\[ k = (2.5)/(√(25)) = (2.5)/(5) = 0.5 \]](https://img.qammunity.org/2024/formulas/physics/high-school/3mqolfv50o0xngjjk1v2d6g9kvkz3r2r1t.png)
Now that you have
, you can use it to find the period
when the length
is 49 in.:
![\[ p' = 0.5 √(49) \]](https://img.qammunity.org/2024/formulas/physics/high-school/tuk3qxlwwtz506hscocb4004fq87rf6qdh.png)
![\[ p' = 0.5 * 7 = 3.5 \, \text{sec} \]](https://img.qammunity.org/2024/formulas/physics/high-school/l6w2zau31gpjb63yupmmtab1omyhj2hps9.png)
Therefore, the period when the length is 49 in. is 3.5 seconds. So, the correct answer is C:
![\[ \text{Period} = 3.5 \, \text{sec} \]](https://img.qammunity.org/2024/formulas/physics/high-school/a9fo4r2zym5pi2mg5diur3jq45udrhsgi5.png)