Question 1026264
the formula is {{{T = 2 * pi * sqrt(L/g)}}}.


i use capital L because it's less easy to be confused with the number one.


what you need to do is solve this equation for L.


the given period is T.


start with {{{T = 2 * pi * sqrt(L/g)}}}.


divide both sides of this equation by (2 * pi) to get:


{{{T / (2 * pi) = sqrt(L/g)}}}.


square both sides of this equation to get:


{{{(T/(2*pi))^2 = L/g}}}.


multiply both sides of this equation to get:


{{{g*(T/(2*pi))^2 = L}}}


that's your answer.


{{{L = g*(T/(2pi))^2}}}


for example, if the given period is 5 seconds, then the formula would becomes:


{{{5 = 2 * pi * sqrt(L/g)}}}.


you would solve for L to get:


{{{L = g*(5/(2pi))^2}}}


since g = 981, the formula would become:


{{{L = 981*(5/(2pi))^2}}}


this results in L = 621.2255072 centimeters.


if you go back to the original formula, then it becomes:


{{{T = 2 * pi * sqrt(621.255072/981)}}}.


that results in T = 5.


any discrepancy will be due to rounding.


i used internally stored numbers and the answer came exactly to 5.


the number of 621.255072 that you see has been rounded to the number of digits that the calculator can display.


using that only will give you an answer that is close to 5, but not right on.