# Length ratios help

1. Aug 7, 2006

### teng125

a pendulum with the length (1) = 100 cm has a period of T(1).
What length (2) is needed to increase the period by
50 s?

i found out that T(1) = 2.0063s
then for T(2),length(2) = 162.071m

i use T = 2pi sqrt(length / gravity)
i think there is smtg wrong with my calculation

can smby pls correct me

thanx

2. Aug 7, 2006

### Staff: Mentor

Not sure what you did. Instead of a lot of calculation, use ratios:
$$\frac{T_2}{T_1} = \sqrt{\frac{L_2}{L_1}}$$

Solve for L_2 in terms of L_1.