Answer:
The length is 5.2 mm.
Explanation:
Given that,
Time period T²= 0.021 s²
Gravity due to acceleration = 9.78 m/s²
We need to calculate the length
Using formula of time period of pendulum
[tex]T=2\pi\sqrt{\dfrac{l}{g}}[/tex]
[tex]l=\dfrac{gT^2}{4\pi^2}[/tex]
Where, l = length
g = acceleration due to gravity
T = time period
Put the value into the formula
[tex]l=\dfrac{9.78\times0.021}{4\times\pi^2}[/tex]
[tex]l=0.0052\ m[/tex]
[tex]l=5.2\ mm[/tex]
Hence, The length is 5.2 mm.