An 8.00 kg stone rests on a spring. The spring is compressed 7.0 cm by the stone.(adsbygoogle = window.adsbygoogle || []).push({});

(a) What is the spring constant?

11.2 N/cm

(b) The stone is pushed down an additional 30.0 cm and released. What is the elastic potential energy of the compressed spring just before that release?

76.7 J

(c) What is the change in the gravitational potential energy of the stone-Earth system when the stone moves from the release point to its maximum height?

76.7 J

(d) What is that maximum height, measured from the release point?

a, b, and c are correct. part d just confuses me.

I said:

[tex]mgh_f - mgh_i = \Delta U_G=76.7J[/tex] (as per part c)

so [tex]mgh_f = 76.7J + mg(-0.37m)[/tex]

so [tex]h_f=\frac{76.7-(8)(9.81)(0.37)}{(8)(9.81)}=0.608[/tex]

Lovely WebAssign puts next to this a lovely red x. Somehow, that makes me wonder if perhaps my answer to part (d) is wrong...

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# Homework Help: Rock on Vertical Spring

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