This is because the swinging motion of a pendulum is due to the force of gravity generated by the earth's size. Other factors, including a pendulum's length, can also affect its motion.

If your pendulum was drawing lines in sand, like Foucault's, n would be the intersection angle between the first line and a line drawn 24 hours later (actually, it's 23 hours, 56 minutes and 4.1 ...

JOHN W. MILES, STABILITY OF FORCED OSCILLATIONS OF A SPHERICAL PENDULUM, Quarterly of Applied Mathematics, Vol. 20, No. 1 (APRIL, 1962), pp. 21-32. ... Steady-state solutions are sought in a ...