Calculate the time period of a simple pendulum whose length is equal to radius of earth.
Hint `: L =R_(e) = 6.4 xx 10^(6) m , g = 9.8 ms^(-2)`
`T ' = 2pi sqrt(( R_(e))/(2g))`

Options

A. Infinity
B. Zero
C. 84.6 minutes
D. 42.3 `sqrt(2)` min

Answer

D

Explanation

`T = 2pi sqrt((1)/(g((1)/(l) + (1)/(R)))) `
l = R
`T = 2pi sqrt((l)/(g((1)/(R) + (1)/(R)))) = 2pi sqrt((R)/(2g)) = 42.3 sqrt(2) min`