A 9-lb collar can slide on a frictionless horizontal rod and is attached to a spring of co...

A 9-lb collar can slide on a frictionless horizontal rod and is attached to a spring of constant k. It is acted upon by a periodic force of magnitude P = Pm sin wft, where Pm = 2 Ib and wf = 5 rad/s. Determine the value of the spring constant k knowing that the motion of the collar has an amplitude of 6 in. and is (a) in phase with the applied force, (b) out of phase with the applied lone.

Fig. P19.101