The radius of the circle along which the trolley moves is r = 40 cm = 0.4 m When the table is rotated, the tension in the spring is equa to the centripetal force, i.e. F =
mv2
r
= mrω2 = 2×0.4×(10)2 = 80 N The extension in the spring is x = 40 - 35 = 5 cm = 0.05 m ∴ Force constant k =