Previously we have discussed energy as the ability to do work. Another way of expressing this is that when we do work, we change the energy of the system.
So it naturally follows that when a satellite is in orbit, it has gravitational energy by way of it position in a gravitational field. Work had to be done on it to get it there. Likewise, if it has a velocity it has kinetic energy
In this section we will explore the concept of energy in the gravitational context.
So it naturally follows that when a satellite is in orbit, it has gravitational energy by way of it position in a gravitational field. Work had to be done on it to get it there. Likewise, if it has a velocity it has kinetic energy
In this section we will explore the concept of energy in the gravitational context.
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In a rush?
Short on time? Here is a brief review of gravitational potential energy. Otherwise , move one |
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Gravitational Potential Energy
Gravitational potential energy (U), or simply Gravitational energy, is due to the work done by a gravitation field.
Previously we have discussed this using the formula
Previously we have discussed this using the formula
U = mgΔh
Unfortunately this formula is a poor model here since it assumes 'g', the gravitational acceleration, is constant.
It is not.
It suffices for small scale situations on earth, but when we look at larger situations, it breaks down.
It is not.
It suffices for small scale situations on earth, but when we look at larger situations, it breaks down.
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This video discusses this concept, allowing for change in gravitational fields and shows, in a simple way how the formula is determined. All this in the context of a teddy bear. |
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Problems to try
- And Earth satellite has a mass of 100 kg and is at an altitude of 2000 km. What is its gravitational energy? (-20.01 GJ)
- The gravitational energy of a Russian Mars orbiter is 4.1 x 1012 J. It orbits Mars at a distance of 4.8×103 km from the centre. What is the mass of the orbiter? (462 kg)
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Total EnergyA satellite in orbit is in motion. This means it has both gravitational potential energy (U) and kinetic energy (K). So how are they related? IF an object increases its gravitational energy , does that mean it will lose kinetic energy? Well that depends - is it in a new orbit, is their work done on it? This video explores the key concepts.
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Sample Problem
We are now ready to try a sample problem
Below is a sample problem with a video that explain how to solve it. It is suggested you try the problem beforehand, as this actually aids understanding, even if you are unsure if you are correct.
We are now ready to try a sample problem
Below is a sample problem with a video that explain how to solve it. It is suggested you try the problem beforehand, as this actually aids understanding, even if you are unsure if you are correct.
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