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Is the textbook wrong or am I?

by drewdiddy
Tags: textbook
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drewdiddy
#1
Oct20-08, 05:02 PM
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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LowlyPion
#2
Oct20-08, 05:18 PM
HW Helper
P: 5,341
Quote Quote by drewdiddy View Post
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.
drewdiddy
#3
Oct20-08, 05:21 PM
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.

LowlyPion
#4
Oct20-08, 05:31 PM
HW Helper
P: 5,341
Is the textbook wrong or am I?

Quote Quote by drewdiddy View Post
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
borgwal
#5
Oct20-08, 08:16 PM
P: 369
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)
LowlyPion
#6
Oct20-08, 08:32 PM
HW Helper
P: 5,341
Quote Quote by borgwal View Post
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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