Levizja
e Planeteve
Levizja
e Planeteve
Gjate çerekut te fundit te shekullit 16 , astronomi Danez Tycho Brahe kreu
vezhgime te kujdeseshme te planeteves gjate nje periode te gjate kohe (20 vjet).
Ai shpresonte qe t'i perdorte keto te dhena per te verifikuar modelin e tij te sistemit diellor,
ne te cilin dielli rrotullohej perreth tokes dhe te gjithe planetet e tjere vertiteshin rreth diellit.
Me vdekjen e Brahes me 1601, asistenti i tij Johannes Kepler trashegoi te dhenat qe kishte grumbulluar Brahes .
Kepleri punoi gati 20 vjet per te analizuar keto te dhena, duke kerkuar ndonje rregullsi matematike.
He came to the conclusion that the ideal of circular orbits should be discarded
and replaced with elliptical orbits.
Kepler summerized his laborious study of planetary motion with the following three laws:
1. The planets move in elliptical orbits with the sun at one focus.
2. A line from the sun to any planets sweeps out equal areas in equal time.
3. The square of a planet's period is proportional to
the cube of the planet's mean distance from the sun.
This java applet let you play with Kepler's laws and learn more physics insight.
Your browser can't run 1.0 Java applets, so here's a picture of the window the program brings up:
The red circle at the center of the screen represent the sun.
The moving yellow circle is the planet.
The initial condition is represented by the blue arrow.
The planet start from the starting point of the blue arrow,
and its initial velocoty is proportional to the length of the arrow.
You can drag the blue arrow to change its initial condition in three different modes:
1. fixed kinetic energy
2. fixed angular momentum
3. arbitrary
Find out the relation between shape and size of the trajectory with the above parameters.
Right click the mouse button to suspend the animation. Click it again to resume.
What if you click it with the left mouse button? Find out by yourself.
Use reset button to clear the screen. (Try to compare different trajectorys before press it!)
You can select four different mode to play with it.
For the energy mode or while you drag the mouse button:
The lower green curve is the potential energy : U(r)=-GMm/r
another one is the effective potential energy Ueff(r)=-GMr/r + L2/(2mr2)
Two horizontal red lines show the total energy of the particle.
(watch the small moving dots! )
The period of the particle motion is also shown in real time unit.
Any suggestions? Please click [email protected]
Personal Home Page for more physics related java applets.
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