Two pendulums with natural frequencies f1 and f2 are released in phase at same instant of time. After what interval will they come in phase again?a) 1/f1 + 1/f2b) 1/f1 - 1/f2c) 1/(f1.f2)d) L.C.M of 1/f1 and 1/f2
d)L.C.M of 1/f1 and 1/f2
CONSIDER THE FOLLOWING CASE
YOU WILL FIND THE THEY HAVE DIFFERNT I.E IF THE FIRST HAS A TIME PERIOD 1/F THE THE SECOND ONE HAS A TIME PERIOD 2/F AND CLEARLY FROM THE FIG. WE CAN GET THAT THE TWO ARE IN PHASE INITIALLY AT t=0 and again come in phase at t=2/F (I.E THE LEAST TIME WHEN THEY START FROM ZERO DISPLACEMENT TOGETHER AND THIS CAN BE MATHEMATICALLY EXPRESSED AS LCM OF THE TWO TIME PERIODS).Hope it's clear now.