If R is the radius of the earth and the acceleration due to gravity on the surface of earth is g = π 2 m s -…

If R is the radius of the earth and the acceleration due to gravity on the surface of earth is g=π2 m s-2, then the length of the second's pendulum at a height h=2R from the surface of earth will be:
  1. 29 m
  2. 19 m
  3. 49 m
  4. 89 m

Solution

Acceleration due to gravity at the given height, g'=GM3R2=19GMR2=19g, where g is acceleration due to gravity at the surface of the Earth.

Now, time period is given by, T=2πlg'

Also the time period of second pendulum is 2 sec.

Therefore, T=2 sec

Then, 2=2πlg×9

l=19 m

Asked in: JEE Main 2024 (01 Feb Shift 1)

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