An 18-lb block A slides in a vertical frictionless slot and is connected to a moving suppo...

An 18-lb block A slides in a vertical frictionless slot and is connected to a moving support B by means of a spring AB of constant k = 10 lb/in. Knowing that the displacement of the support is δ = δm sin ωft, where δm = 6 in., determine the range of values of ωf for which the amplitude of the fluctuating force exerted by the spring on the block is less than 30 lb.

Fig. P19.105