Physics question: gravitation

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1

<p>i try to figure it out, but cannot. someone help plz</p>

<p><a href="http://img295.imageshack.us/img295/7005/physics2sa.png%5B/url%5D"&gt;http://img295.imageshack.us/img295/7005/physics2sa.png&lt;/a&gt;&lt;/p>

<p>answer is D, but why??</p>

<p>based on the equation U = - GMm/r, when objects are released, as the r decrease, G, M, m are constants. U approaches 0.................</p>

2

<p>No, U is initially zero and approaches negative infinity.</p>