Posted by **Dwayne** on Monday, May 2, 2011 at 11:35am.

Law of Gravitation- Find an expression for the magnitude of the initial velocity that a projectile must possess in order to leave the earth when air friction is neglected.

The gravitational constant for g is, G = 6.67428*10^-11 m^3 Kg^-1 s^-2

Please answer the question fully and please give any helpful websites, thankyou.

Also I know calculus.

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**bobpursley**, Monday, May 2, 2011 at 11:39am
Then set the initial KEnergy equal to the potential energy at the surface of EArth.

1/2 mv^2= GMe*m/re

solve for escape velocity, v

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**Dwayne**, Monday, May 2, 2011 at 11:48am
v^2 = 2Mg/r + (u^2 -2Mg/d )

Is that right

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**bobpursley**, Monday, May 2, 2011 at 12:00pm
Why did you make it so complicated?

1/2 m v^2=GMe m/re

v^2= 2GMe/re

take the square root of each side.

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