<p>Since you're already at Cornell, you can probably get a better answer from your advisor, if s/he is in the Mech Eng department. Admissions is done by each department rather than by a university adcom like in undergrad admissions. </p>
<p>The GRE probably won't affect your chances of admission by much. As an engineering major, you'll probably score at least a 750 on the quant section. As for the writing and verbal sections, you'll do good enough because I can already see that you can read and write. Engineering grad schools don't really care much for these sections unless you have an extremely poor score.</p>