Q.
Two simple pendulums whose lengths are 100cm and 121cm are suspended side by side. Their bobs are pulled together and then released. After how many minimum oscillations of the longer pendulum, will be the two be in phase again?
The time period of a simple penduium is T=2πgl
where, I is length. ∴T2T1=l2l1
Given, l1=100cm,l2=121cm ∴T1T2=100121=1011.
In a given time shorter penduium will make one oscillation more than the longer.
Let after n oscillations, the pendulums are in same phase, then n×11=(n+1)×10 ⇒n=10