Question

A pendulum completes 2 oscillations in 5 s . If g= 9.8 ms-2 find its length.

Answer 1

we know that time period of a simple pendulum
T=2π√l/g
squaring on both sides , we get
T^2= 4π^2(l/g)
from here
l =(T^2×g)/4π^2
given that
T=5s for two oscillations
so, for one oscillation T=5/2=2.5s
g=9.8 m/s^2
so,
l = (5^2×9.8)/4×3.14^2
=6.2mts

Answer 2

T=2π√l/g
squaring on both sides , we get
T^2= 4π^2(l/g)
from here
l =(T^2×g)/4π^2
given that
T=5s for two oscillations
so, for one oscillation T=5/2=2.5s
g=9.8 m/s^2
so,
l = (5^2×9.8)/4×3.14^2
=6.2mts