Time period, T = 2π sqrt(l/g)Time period of the pendulum when the lift moves upward with an acceleration ‘a’ = 2π sqrt(l/(g+a))We have, T = 4sec = 2π sqrt(l/10) ------------------(1)= 2π sqrt(l/(10+4)) -----------(2)’ , T2When acceleration upward with a= 4m/sDivide the equation (2) by (1) / 4] = [sqrt (10/14)]’[T = 4* [sqrt (10/14)] = 3.38 sec2 [1] Therefore, time period of the pendulum when the lift moves upward with an acceleration of 4m/sTime period of the pendulum when the lift moves downward with an acceleration ‘a’ = 2π sqrt(l/(g-a)) = 4* [sqrt (10/6)] = 5.16 sec2 Proceeding as mentioned above, we get: [2] Time period of the pendulum when the lift moves upward with an acceleration of 4m/s