(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

A projectile of mass, m is fired from the surface of the earth at an angle alpha from the vertical. THe initial speed v0 is equal to (GM/R)^0.5 where G is gravitational cont, M is mass of earth and R is radius of the earth. How high does the projectile rise? Neglect air resistance and the earth's rotation. r.max=r max in picture.

http://img370.imageshack.us/my.php?image=quesgf6.jpg

http://img370.imageshack.us/img370/189/quesgf6.jpg [Broken]

http://g.imageshack.us/img370/quesgf6.jpg/1/ [Broken]

2. Relevant equations

U + K = constant

3. The attempt at a solution

So I started with that equation, and find out that

-(GMm/R) + .5(m)(v0^2) = -(GMm/(r.max)) + .5(m)(vf^2)

and from here we can eliminate the vf because it is zero when it is a the highest position. But after substitution that v0 = (GM/R)^0.5 this equation will become

-(GMm/R) + .5(GMm/R) = -(GMm/(r.max))

this will become r.max =2R which i think is impossible.

Can anyone out there here me ? I am totally clueless. From the lecturer I found out that is it max when alpha is = 60degrees and the r.max is (3R/2) .

Thanks in advance

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# Homework Help: Projectile Motion in Bigger Radius.

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