ICSE Class 9 Physics Question 14 of 20

Measurements and Experimentation — Question 8

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8
Question

Question 1(viii)

The length of a simple pendulum is made one-fourth. Its time period becomes —

  1. four times
  2. one-fourth
  3. double
  4. half
Answer

half

Reason — Time period of a simple pendulum is given by:

T=2πlg\text T = 2 \text π \sqrt{\dfrac{\text l}{\text g}} \\[0.5em]

Time period is directly proportional to the square root of the length of the pendulum.

In the case when length is made one-fourth, we see that —

T=2πl4×gT=22×πlgT=πlg\text T = 2 \text π \sqrt{\dfrac{\text l}{4\times \text g}} \\[0.5em] \text T = \dfrac{2}{2} \times \text π \sqrt{\dfrac{\text l}{\text g}} \\[0.5em] \text T = \text π \sqrt{\dfrac{\text l}{\text g}} \\[0.5em]

Hence, we can say that when the length is made four times, time period of a simple pendulum is reduced to half.