- #1
HunterDX77M
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Homework Statement
A 20 kg mass is attached to a 120 N/m spring and is free to slide across a horizontal
frictionless surface. If the spring is originally at its equilibrium length when the mass is given an initial velocity to the right, after how much time is the spring once again at its equilibrium length?
Homework Equations
Fs = -kx
ω2 = k/m
The Attempt at a Solution
Well I thought that I'd just get ω and solve the simple equation. But I'm not getting the right answer.
[tex]\omega = \sqrt{120/20} = \sqrt{6}[/tex]
[tex]x(t) = Acos(\omega t) = 0 [/tex]
[tex]0/A = cos(\omega t) = 0 [/tex]
[tex]arccos(0) = \omega t[/tex]
[tex]\pi \div 2 = \omega t[/tex]
[tex]t = \frac{\pi}{2 \sqrt{6}} = 0.641 s [/tex]
But the correct answer is twice that. Why?