So I’m confused. I saw this and initially thought it was just a matter of circumference. Suppose the radius of circle A is 10 and the radius of circle B is twice that amount, so it’s 20
The formula to find the circumference of a circle is C = 2πr
So for circle A;
2π10 = 62.831
And for circle B;
2π20 = 125.663
Then to find the difference in circumferences, divide them
125.663/62.831 = 2.000
Therefore, it should take two rotations to rotate one circle around the other
What am I getting wrong here?
Booooo
This video didn’t give the correct answer in any place reasonable. I just wanna know the answer before you go off on an 18 minute lecture.
To anyone who just wants to know the answer without watching the whole video, the correct answer is 4
https://www.nytimes.com/1982/05/25/us/error-found-in-sat-question.html
How did this video stretch out to 18 mins?
I remember a mindyourdecisions yt video about this from several years ago that showed it in a couple of minutes and why it is n+1.
sorry i don’t remember the url though.
It explains the answer is 4 before the 5 minute mark.
Part of the reason is because it goes into the story of the SAT being wrong and a student being the one to catch it, which I found interesting.
After that it mathematically proves it several different ways and then shows how it relates to some real problems in astronomy.
Godamn thats a phenominal example of reletivity.
I did not watch this video but did read about this math. Visualize the larger circle unwrapped into a flat line, and the smaller circle sliding along the length of the line so its bottom point is fixed to the line. You’ll see the small circle never rotates. Now slide the small circle with a point fixed onto the large circle in the same way, and you’ll see the small circle makes one complete rotation. That rotation happens in addition to the rotations you get from dividing the larger circumference by the smaller circumference, so the answer is 4 in this case
if the path had been straight yeah, but the path itself rotates 360 degrees, which gives us an extra rotation
The center travels 2π per rotation but need to travel 8π because the path of the center of the small circle is a circle 4r the radius of the large circle plus the radius of the small circle. It would be three if the center of the small circle traveled along the edge of the larger circle but it’s edge to edge.
That’s what you’d think, but there’s an extra rotation involved in the act of the small circle moving around the larger circle rather than along a straight line, so it’s (6π/2π) + 1
VG video. Confused by the word ‘revolve’? How many times does the Earth ‘revolve’ around the Sun in a year?
But, worse yet, there were THREE correct answers … none listed!
