Two the same coins, one of which (set to a) keeps moving, the other (set to b) close to a scrolling, ask the B itself a few weeks after running around A, B itself has been rotated for a few weeks (360 degrees for one week )?
What is interesting is that many people feel that "B rotation one week", the reason is the circumference of the two coins. In fact, the two coins will be tried, and they will know that the coin b is actually 720 degrees. Some people will do it in two weeks. This phenomenon is not understood. If a coin is rolled on a week, it rolls The distance is exactly the circumference of the coin (this is correct), and the coin B rolls along the coin A, the truth is the same.
In fact, this is two things, the so-called "coin rolls on a flat place, and it moves the distance is the circumference of the coin." This distance refers to the horizontal distance on the flat, instead, it is the point of coins and ground contact. And the coin is around a point A. The trajectory it has passed is not horizontal, but two parabolic.
If the center of the round diameter and the moving medium of the circle and the movement of the small circle are 1: 1, the small circle will rotate 2 laps (720 degrees), if it is 2: 1, the small circle will turn 3 turns; If it is 3: 1, it is 4 laps, 4: 1 is 5 laps ... actually a radius added, if the small circle is attached to the large circle, it is a radius, huh, huh.
Comparing the cattle people will use the formula to calculate the red dot trajectory, I see the dizzy: http://mathworld.wolfram.com/epiCloid.html
There is also a more interesting thing. For a long time, the painters observe the carriage of the carriage, the upper half of the wheel and the lower half of the wheel, when the carriage ran, the upper part of the spokes It will be unclear, and the spokes of the lower half are relatively clear. Therefore, the person who is drawn is written, and when the mobile carriage or bicycle, it will only take the radiation of the lower half of the wheel.
When I heard it, I also felt incredible, I specially ran to the street to see the automatic car. Sure enough, I launched it in the paper, I understand that the speed of each point on the wheel is definitely the same, but Every point is different from the observer. In the same time, the upper part (relative to the roadside observer) is longer than the distance from the lower half ... Who is a reference:
