I'd be grateful if someone can help me with this problem -(adsbygoogle = window.adsbygoogle || []).push({});

Zero, a hypothetical planet, has a mass of 4.4 × 10^23 kg, a radius of 3.2 × 10^6 m, and no atmosphere. A 2.4 kg space probe is to be launched vertically from its surface.(a)If the probe is launched with an initial energy of 7.4 × 10^7 J, what will be its kinetic energy when it is 4.8 × 10^6 m from the center of Zero?(b)If the probe is to achieve a maximum distance of 8.9 × 10^6 m from the center of Zero, with what initial kinetic energy must it be launched from the surface of Zero?

I started out by using the equation for energy which isE = KE + U(kinetic energy plus potential energy).

So I got 7.4x10^7 = KE + (mGR). But I have 2 main problems: one is, do I use G = 6.67x10^-11? The second question is, I know there is something I have to do with the radius, but I don't exactly know what. Do I domass of probe/R? I did that but still got the answer wrong...I know I'm doing something wrong with the radius.

Thanks a lot.

*If I get parta, I'm sure I can get the second part by myself.

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# Homework Help: Gravitational Potential Energy of a planet

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