What is the Maximum Height Attained by an Object Launched from Earth's Surface?

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SUMMARY

The discussion focuses on calculating the maximum height attained by an object launched vertically from Earth's surface with an initial speed \( v_i \) that is less than the escape speed \( v_{esc} \). The derived formula for maximum height \( h \) is given by \( h = \frac{R_E v_i^2}{v_{esc}^2 - v_i^2} \). The conversation highlights the application of conservation of energy principles, specifically the relationship between kinetic energy and gravitational potential energy, to derive this equation. The confusion arises from a specific step in the derivation involving the transformation of energy equations.

PREREQUISITES
  • Understanding of gravitational potential energy and kinetic energy concepts
  • Familiarity with the conservation of energy principle
  • Basic knowledge of algebraic manipulation of equations
  • Awareness of escape velocity calculations
NEXT STEPS
  • Study the derivation of escape velocity \( v_{esc} = \sqrt{\frac{2GM_E}{R_E}} \)
  • Learn about energy conservation in gravitational fields
  • Explore the implications of launching objects at various speeds relative to escape velocity
  • Investigate the effects of air resistance on maximum height calculations
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Students in physics, educators teaching mechanics, and anyone interested in understanding projectile motion and gravitational effects on launched objects.

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Homework Statement


An Object is fired vertically upward from the surface of the Earth ( of radius RE ) with an initial speed vi that is comparable to but less than the escape speed vesc

Show that the object attains a maximum height h given by h=\stackrel{R_{E}v^{2}_{i}}{v^{2}_{esc}-v^{2}_{i}}

Homework Equations


The Attempt at a Solution


I have the solution but I am confused with a step.
Here is the solution provided up until the step on which I am confused:

(K+U_{g})_{f}=(K+U_{g})_{f}

\stackrel{1}{2}mv^{2}_{i} - \stackrel{GmM_{E}}{R_{E}} = 0 - \stackrel{GmM_{E}}{R_{E}+h}

where \stackrel{1}{2}mv^{2}_{esc}= \stackrel{GmM_{E}}{R_{E}}

Then\stackrel{1}{2}v^{2}_{i} - \stackrel{1}{2}v^{2}_{esc}= -\stackrel{1}{2}v^{2}_{esc} (\stackrel{R_{E}}{R_{E}+h})

So the jump I am confused about is the equation that follows the "Then" Statement. I'm not sure why this is true.

(sorry for the poor look of the equations. Hopefully its readable, I wasn't sure how to make fractions.)
 
Last edited:
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\frac x y

\frac x y

And if not absolutely necessary don't put LaTeX inline, it looks better in its own lines.
 

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