A 20-kg block is attached to a spring of constant k = 8 kN/m and can move without friction...

A 20-kg block is attached to a spring of constant k = 8 kN/m and can move without friction in a vertical slot as shown. The block is acted upon by a periodic force of magnitude P = Pm sin ωf t, where Pm = 100 N. Determine the amplitude of the motion of the block if (a) ωf = 10 rad/s, (b) ωf = 19 rad/s, (c) ωf = 30 rad/s.

Fig. P19.99