Posted by **rick** on Monday, February 14, 2011 at 7:47pm.

A 3Kg projectile is fired straight upward from earth's surface with a speed that is one-fourth the escape speed. Neglecting air resistance.

a) What is the Kinetic energy of this projectile when it is launched?

b) what is the gravitational potential energy of this projectile when it is launched?

c) what is the total mechanical energy of this projectile?

D) what is the highest altitude reached by this projectile, measured from the earth's surface.

Now I know how to solve part A, and part c is part A + part B, I know part B

- physics -
**rick**, Monday, February 14, 2011 at 7:49pm
I know part B formula but I don't know which mass to plug in for m2? I have no idea how to solve part D? please help.

- physics -
**tchrwill**, Tuesday, February 15, 2011 at 5:16pm
Escape velocity is 36,685fps.

36,685/4 = 9171.25fps.

From Vf = Vo - gt, 0 = 9171.25 - 32.2t making the time to Vf = 0 284.82sec.

The height reached then derives from

h = Vo(t) - gt^2/2 =

...9171.25(284.820 - 32.2[(284.82)^2]/2

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