What is the magnitude of the angular momentum of the particle about the center of the circle as a
function of time?
(A) mbt/r
(B) mbrt
(C) (mbr^2)t
(D) (mb^2)rt^2
(E) (mb^2)(r^2)(t^2)

Suppose that 27 j of work is needed to stretch a spring from its natural length of 6 m to a length of 9 m. (a) how much work is needed to stretch the spring from 12 m to 14 m? j (b) how far beyond its natural length will a force of 78 n keep the spring stretched?