What is the acceleration value i'll give extra is you are right

Hydrogen and helium are both members of?

Determine the age of a fossil if it had only one eighth of its original carbon-14 content remaining?

The period of a pendulum varies directly as the square root of the length of the pendulum and inversely as the square root of the acceleration due to gravity. find the period when the length is 144 cm and the acceleration due to gravity is 980 cm per second squared, if the period is 7pi seconds when the length is 289 cm and the acceleration due to gravity is 980 cm per second squared.