Is the textbook wrong or am I?

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The discussion revolves around a physics problem involving a vertical spring and the speed it can impart to a ball when released. The initial calculations yield a velocity of 7.68 m/s, while the textbook states it should be 7.47 m/s. Participants clarify that the conservation of energy equation must account for gravitational potential energy, leading to the conclusion that the textbook's answer is correct. One participant acknowledges the error in their terminology regarding vertical distance. Ultimately, the consensus is that the textbook's calculation is accurate.
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Homework Statement



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?


Homework Equations



Conservation of Energy using 1/2 k x^2 for Uspring.

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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drewdiddy said:

Homework Statement



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?


Homework Equations



Conservation of Energy using 1/2 k x^2 for Uspring.

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.
 
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.
 
drewdiddy said:
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
 
Last edited:
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)
 
borgwal said:
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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