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I am having diffculty with a physics problem. If anyone could help me out it would be greatly appreciated.

Question:

One end of a long elastic cord is tied to the railing of a high bridge. The other end is tied to a sandbag with a mass of 23.2 kg. The unstretched length of the elastic cord is 5.44 m and its force constant is 382.0 N/m. The sandbag is dropped from the railing. How far does it drop before coming to rest momentarily before being pulled back up by the cord.

My answer, so far:

Known: k=382.0 N/m; Xinitial = 5.44 m; m of bag = 23.2 kg.

Unknown: Xfinal = ?; W =?

I know that W = F(Xfinal) and that W = Efinal - Einitial

Therefore,

F(Xfinal) = Efinal - Einitial

F(Xfinal) = 1/2k(Xfinal)^2 - 1/2k(Xinitial)^2

228 N (Xf) = 1/2(382.0 N/m)(Xf^2) - 1/2(382.0 N/m)(5.44 m)^2

By rearranging and solving for Xf

Xf = -4.87 m; +6.09 m

Rejecting -4.87 m, my answer is 6.09 m, however it is not right.

Does anyone see what I have done wrong??

If anyone could help me out, it would be greatly appreciated.

Thanks

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