Good Day Prof Biezen, in your video 5;29 you mentioned ratio of T square by R cube is always equal to 1.Could you please explained more details why is always equal to 1?is this also for other planet like Saturn, Uranus or mercury and venus? Happy Thanksgiving Day and have a nice weekend.. 👍👍
Yes, when we use "astronomical units" for distance and "years" for time, Kepler's 3rd law simplifies to the ratio of T^2 / R^3 = 1 for all the planets in our solar system.
Michel,it seems like American schools are hostile to the idea of the centrifugal "psuedoforce ". I like it because it is descriptive of the force diagram.
I think it is up to the individual teacher or professor and not a universal condition in all schools. I know a few professors who do not like to use "centrifugal" force.
Probablly yes, but then i still don’t understand the following: In the formula (2:58) you are multiplying the G constante with the mass of earth. And when you eventually put the numbers in your calculator, you say: 4π squared devided by G and again devided by M. Why was it not 4πsquared /G•M?
The orbits are indeed elliptical and not circular. If you are interested in Kepler's equations for elliptical orbits, we have videos on that in our Astrophysics playlist. The centrifugal force is indeed a fictitious force (doesn't exist) just like the Coriolis force, but thinking of them as forces helps us solve problems.
Keppler's second law in essence is a formulation of the conservation of angular momentum. The third law simply states the relationship between the orbital period and the orbital radius.
I have the same question. I notice that in 2nd kepler's law: conservation anguler momentum, r is inversely proportional to v. But, in 3rd kepler's law, r is inversely proportional to square of v
For the velocity equation, why did you use d = 2*pi*r instead of the perimeter equation for an ellipse (d ≈ 2*pi*sqrt[ (a^2+b^2)/2 ] or even a series expansion)? that would give you a slightly better approximation for the AU, right?
gulfcoaster5 Using the perimeter of a circle is good enough for illustration. The difference between the circumference of a circle and of an ellipse at the eccentricity of the Earth is very small. Go ahead and calculate it, you'll see.
The standard units is seconds and that is what is used in all the equations. Sometimes it is easier to relate to the time by converting it to days or years.
The centripetal force (center seeking force) acts inward and is caused by the force of gravity. The fictitious (non-existing) force called the centrifugal force has the same magnitude as the centripetal force but is thought of as acting outward because of the sensation that objects are pushed outward when they travel in a circle.
How come at 3:16 you said we're going to multiple the gravitation constant to the mass of the Earth, but at 3:30 you say we're using the mass of the Sun?
OK fine Kepler gave a law. A useful law. But why do we have to prove it? Cant we just trust the poor man? I hate proving things already proven by others
many experiments are made from the hypothesis, we keep testing it because we want to improve the efficiency result ( chemistry) or accurate law ( physics) . Nothing is 100% and a man-made theory could be imperfect for all objects
