The length of the second's pendulum is decreased by 0.3 cm, when it is shifted to Chennai from London. If the acceleration due to gravity at London is `981" cm"//"s"^(2)`, the acceleration due to gravity at Chennai is (Assume `pi^(2)=10`)

Options

A. `981" cm"//"s"^(2)`
B. `978" cm"//"s"^(2)`
C. `984" cm"//"s"^(2)`
D. `975" cm"//"s"^(2)`

Answer

B

Explanation

Length of the pendulum
`L_(1)=(g_(1)T^(2))/(4pi^(2))=(g_(1))/(pi^(2))"and"L_(2)=(g_(2)T^(2))/(4pi^(2))=(g_(2))/(pi^(2))`
Since, length is decreased, `g_(2)` is less than `g_(1)`.
`:." "L_(1)-L_(2)=(g_(1)-g_(2))/(pi^(2))`
or `" "(L_(1)-L_(2))pi^(2)=g_(1)-g_(2)`
or `" "0.3xx10=g_(1)-g_(2)`
`:.g_(2)=981-3=978" cm"//"s"^(2)`