Two pendulums of time periods 1.8 s and 2 s are set into oscillation at the same time. After how many seconds will the faster moving pendulum execute one complete oscillation more than the outher? How many complete oscillations will the faster moving pendulum execute during this time?

Explanation

Suppose the faster pendulum executes one more oscillation than the other after t s.
Number of complete oscillations of the first pendulum in t s = `t/1.8`.
Number of oscillations of the second pendulum in t s = `t/2`.
According to the given condition, `t/1.8-t/2=1`
or, `0.2t=2xx1.8or,t=18s`
Number of complete oscillations executed by the faster pendulum (time period 1.8 s) = `18/1.8=10`.