7.2.3-4 Gravitational Potential and Orbits of Planets and Satellites

18 flashcards · Physics · by TheoTyson

1. What is gravitational potential?

   The ​work done per unit mass when moving an object from infinity to that point

2. What is the gravitational potential at a point an infinite distance from the mass?

   Zero gravitational potential.

3. What is the gravitational potential - radius\text{gravitational potential - radius}gravitational potential - radius graph?

4. What is the escape velocity?

   The velocity at which an object's kinetic energy is equal to minus its gravitational potential energy.

5. What is gravitational potential difference?

   The energy needed to move a unit mass between two points.

6. What are equipotentials?

   Surfaces that join all of the points with the same potential, so no energy is lost or gained moving along the surface.

7. What is the relationship between equipotentials and field lines?

   Equipotentials and field lines are perpendicular.

8. What is the area under a gravitational field strength - radius\text{gravitational field strength - radius}gravitational field strength - radius graph?

   The gravitational potential difference.

9. Why is gravitational potential negative?

   The work needs to be done against the gravitation field to move an object out of it.

10. What is the relationship between Period\text{Period}Period and radius\text{radius}radius ?

    T2∝r3\text{T}^2 \propto \text{r}^3T2∝r3

11. What is the relationship between velocity\text{velocity}velocity and radius\text{radius}radius ?

    v∝1r\text{v} \propto \frac{1}{\sqrt{\text{r}}}v∝r ​1​

12. What is the derivation of the equation for orbital period?

    The centripetal force is equal to the gravitational force. mv2r=GMmr2\frac{mv^2}{r} = \frac{GMm}{r^2}rmv2​=r2GMm​ , rearrange for v, v=GMrv = \sqrt{\frac{GM}{r}}v=rGM​ ​ . v=2πrTv = \frac{2 \pi r}{T}v=T2πr​ , T=2πrvT = \frac{2 \pi r}{v}T=v2πr​ . T=2πrrGMT = \frac{2 \pi r \sqrt{r}}{\sqrt{GM}}T=GM ​2πrr ​​ , T2=4π2r3GMT^2 = \frac{4 \pi^2 r^3}{GM}T2=GM4π2r3​ .

13. What is the energy of an orbiting satellite?

    The energy is constant, the sum of kinetic energy and potential energy is the same.

14. What does a geostationary satellite do?

    Orbits the Earth once in 24 hours, stays at the same point above Earth.

15. What is a synchronous orbit?

    An orbit where the orbital period is the same as the rotational period of the orbited object.

16. What does a low orbit satellite do?

    Orbits between 180-2000km above the Earth, always over a new part of the Earth.

17. What is the plane and function of geostationary satellites?

    The plane follows the Earth's equator, the function is for TV and telephone signals.

18. What is the plane and function of low orbit satellites?

    The plane includes the North and South Pole, the function could be as an imaging satellite.