Suppose a 300g mass is dropped from a height of 40cm onto a vertical spring with spring constant 200N/m (having a light platform on top) and sticks to the platform (a) How far will the spring compress? (b) How far will the spring be stretched as the mass and spring rebound? use S.I. units.(adsbygoogle = window.adsbygoogle || []).push({});

I can do part (a) ans = .124m. For part (b) I cannot get right answer =.095m

Us at the bottom = Ug at end

where: Us = potential energy of the spring

Ug = potential energy of gravity

this gives:

.5kx^2 = mgx

=> .5kx = mg

= wrong result

what am I missing,

Thanks & regards

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# Spring energy question

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