# Math BOBPURSLEY HELP HELP HELP HELP

posted by Dwayne

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

Also I know calculus.

1. bobpursley

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

2. Dwayne

v^2 = 2Mg/r + (u^2 -2Mg/d )

Is that right

3. bobpursley

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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