# Is the textbook wrong or am I?

by drewdiddy
Tags: textbook
 P: 13 1. The problem statement, all variables and given/known data A vertical spring (ignore its mass), whose spring constant is 875 N/m is attached to a table and is compressed down by .160 m. (a) What upward speed can it give to a .380 kg ball when released? 2. Relevant equations Conservation of Energy using 1/2 k x^2 for Uspring. 3. The attempt at a solution I get 7.68 m/s for the velocity and the book gets 7.47 m/s. Wanted to see who was right and if I'm doing something wrong.
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P: 5,346
 Quote by drewdiddy 1. The problem statement, all variables and given/known data A vertical spring (ignore its mass), whose spring constant is 875 N/m is attached to a table and is compressed down by .160 m. (a) What upward speed can it give to a .380 kg ball when released? 2. Relevant equations Conservation of Energy using 1/2 k x^2 for Uspring. 3. The attempt at a solution I get 7.68 m/s for the velocity and the book gets 7.47 m/s. Wanted to see who was right and if I'm doing something wrong.
"Upward" also means against gravity. You should also figure as an adjustment the m*g*h over the displacement of the acceleration.
 P: 13 So you're saying you got the book's answer? I used the conservation of energy subbing values for spring and taking into account y=0 when crossing the original spring length. I'm quite sure I have the right answer and the book's is wrong but I just want to verify.
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P: 5,346

## Is the textbook wrong or am I?

 Quote by drewdiddy So you're saying you got the book's answer? I used the conservation of energy subbing values for spring and taking into account y=0 when crossing the original spring length. I'm quite sure I have the right answer and the book's is wrong but I just want to verify.
I'm just saying that

mv2/2 = kx2/2 - m*g*x
 P: 370 You are wrong, your book is right, Pion is right: (except I would not use both "h" and "x", there is only one vertical distance in the problem)
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P: 5,346
 Quote by borgwal You are wrong, your book is right, Pion is right: (except I would not use both "h" and "x", there is only one vertical distance in the problem)
Thanks for the catch. Of course h and x are the same.

I edited the previous post to be correct now.

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