A set of coupled pendula has m = 0:2kg for both masses, but k and l are unknown. At t = 0, the left hand mass is held at xL = 2:5cm and the right hand mass is held at xR = 0. The masses are then released. At rst, the left hand mass oscillates with a period of 1:1s, and the right hand mass is nearly motionless. At t = 10s, the two masses are oscillating at nearly equal amplitudes. At t = 20s, the right hand side mass is oscillation strongly and the left hand one is nearly motionless. At t = 30s, the two masses are oscillating with approximately equal amplitude. At t = 40s, the left mass is oscillating strongly, and the right mass is nearly motionless. Find the approximate values of k and l.