Select the correct answer from each drop-down menu. Two magnets are placed as shown in the image.

The force of (blank) between the poles B and C is (blank). And the force of (blank) between the poles A and D is (blank).

The period of a pendulum varies directly as the square root of the length of the pendulum and inversely as the square root of the acceleration due to gravity. find the period when the length is 144 cm and the acceleration due to gravity is 980 cm per second squared, if the period is 7pi seconds when the length is 289 cm and the acceleration due to gravity is 980 cm per second squared.