You are on Pluto and would like to send a probe into space so that it does not fall back to the surface. What minimum launch speed do you need? (The mass of Pluto is 1.3x^22 kg and the radius of Pluto is 1.18x10^6 m).

Question

You are on Pluto and would like to send a probe into space so that it does not fall back to the surface. What minimum launch speed do you need? (The mass of Pluto is 1.3x^22 kg and the radius of Pluto is 1.18x10^6 m).
Answer in km/s. 
I have used the velocity of escape = (square root of) 2(g)(m1)(m2)/r but keep getting the wrong answer. 
1.21e5 km/s and 4.7e3 km/s are two of the answers I've been getting. Help?

bobpursley · Answer

PE at surface=KE at launch
GMp/radius = 1/2 v^2

v= sqrt(2GMp/r) where G is 6.67E-11

v=sqrt(2*6.67E-11*1.3E22)/1.18E6)

You seem to have difficulty operating your calculator. Put this into the Google search window:
sqrt(2*6.67E-11*1.3E22/1.18E6)

Laramie · Answer

Hmm. I wonder how I can correct my poor usage. Thank you very much!