How much work is done when a satellite is launched into orbit?

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SUMMARY

The discussion centers on calculating the work required to launch a 1000 kg satellite into a geostationary orbit at an altitude of 35,800 km above Earth's surface. The work is computed using Newton's law of universal gravitation and the formula for work, resulting in an initial calculation of approximately 5.3108 x 1010 Joules. However, the textbook suggests a value of 5.77 x 1010 Joules, indicating a need to include kinetic energy in the total work calculation. The kinetic energy formula, Ekinetic = 1/2 mv2, is essential for determining the total energy required for the satellite to maintain its orbit.

PREREQUISITES
  • Newton's law of universal gravitation
  • Work-energy principle
  • Kinetic energy formula
  • Understanding of geostationary orbits
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  • Study the derivation of kinetic energy from Newton's second law (F = ma)
  • Research the mechanics of satellite motion in geostationary orbits
  • Explore gravitational potential energy calculations in astrophysics
  • Learn about the energy requirements for launching satellites using propulsion systems
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tuki
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Homework Statement


A Satellite is brought up into a geostationary orbit (altitude 35800km measured from the surface of the earth). Satellite weights 1000.0kg. How much work is required to bring satellite from a surface of the Earth to
geostationary orbit?

Homework Equations


Newton's law of universal gravitation
$$ F = G \frac{m_1m_2}{r^2} $$
Work is defined as:
$$ W \int F \cdot s ds $$

The Attempt at a Solution


I want to compute work done by Newton's law of universal gravitation when
moving satellite from the surface of the Earth to the orbit. It should be done with:h0 is surface of the Earth (about 6371 km)
h1 is geostationary orbit (about 6371 km + 35800 km = 42171km)
m1 is mass of the satellite (about 1000 kg)
m2 is mass of the Earth (about 5.972E24)

$$ W = \int_{h_0}^{h_1} G \frac{m_1 m_2}{r^2} dr = - G \frac{m_1 m_2}{h_1} - (- G \frac{m_1 m_2}{h_0} $$
$$ = G m_1 m_2 (\frac{1}{h_1} - \frac{1}{h_0}) \approx 5.3108\cdot 10^{10} \text{ J} $$

However, our textbook suggests that the correct answer would be 5.77E10 Joules. I can't exactly spot out where the mistake is.
 
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Is giving the satellite potential energy the only thing you need to do to put it in geostationary orbit?
 
Orodruin said:
Is giving the satellite potential energy the only thing you need to do to put it in geostationary orbit?
Yes you would need the velocity too in order to stay in orbit.
 
Can you see that that's your answer, or is still unclear?
 
Bandersnatch said:
Can you see that that's your answer, or is still unclear?
Yes, I can get the correct answer by adding kinetic energy from the speed $$ E_{kinetic} = \frac{1}{2} mv^2 $$ to the potential energy I already computed. I wonder if it would be possible to derive the work required to accelerate an object to a given speed (when mass is known) starting from Newton's second law? $$ F = ma $$ I mean you start from Newton's second law and end up with a formula for kinetic energy?
 
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tuki said:
I wonder if it would be possible to derive the work required to accelerate an object to a given speed (when mass is known) starting from Newton's second law?
F=maF=ma​
F = ma I mean you start from Newton's second law and end up with a formula for kinetic energy?
Why don’t you try and see what you get?
 

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