1. The problem statement, all variables and given/known data A block of mass 2kg is suspended from a fixed support by a spring of strength 2000N/m. The block is subject to the vertical driving force 36cos(pt)N. Given that the spring will yield if its extension exceeds 4 cm, find the range of frequencies that can safely be applied. 2. Relevant equation x''+2kx'+w^2x=F(t) p is angular frequency 2mk is the damping constant mw^2 is the spring constant mF(t) is the driving force 3. The attempt at a solution I think this system is undamped so then k=0. Now I have x''+xw^2=F(t) So w^2 = 2000 and F(t)=36cos(pt) with this we have a formula for the amplitude which is a = 36/([(2000-p^2)^2]^1/2) So I want the amplitude to be -4<=a<=4 rearranging I get p<=(1991)^1/2 and p>=(1991)^1/2 but my book says the answer is p<20rads/s and p>40rads/s what am I doing wrong? should I have gravity in there somewhere?