Would it be correct to assume that when one full rotation of the larger circle has happened from our perspective, the smaller circle has not yet completed a full rotation in the sense that not every point on its circumference has touched the larger circle?
In other words, it has returned to its starting position from our point of view, but it has not actually completed one full rotation.
@orgANGmo Says:
My brain just melted a little. Thanks.
@ontheothersideof Says:
THE PERSPECTIVE OF THE CIRCLE IS THE ONLY ONE THAT MATTERS. The only way the "human" perception yields the answer 4 is because you know (from the big A on the circle) which way the circle has it's "up". Remove the annotation, and even from the human perspective you get 3.
@highviewbarbell Says:
Guess: the answer should be 4
@morrígan_band_official Says:
so makhnovschina, then 1936... so we've got two
@MathTitan28 Says:
mas os 3 alunos tbm não sabiam que era 4
@shreerajPatil-h9s Says:
THe answer is 2/3
@hcgreier6037 Says:
I'm hair splitting now, I know:
365.24 × 24 = 8765.76
366.24 × 23.93444444 = 8765.750933
Difference Δ = (8765.76 − 8765.750933)d · 1440 m/d = 13.06 m
Cosidering astronomy, there are "many" years:
• Julian year: 365.25 days = 365d 6h (exactly)
• Tropical year: 365.2421897 days = 365d 5h 48m 45.19s
• Siderial year: 365.256363 days = 365d 6h 9m 10s
• Anomalistic year: 365.259636 days = 365d 6h 13m 53s
Lookup the internet for details ;)
@swarnavvv Says:
and a modified version of this question came in JEE Adv 2026 this year. (Q1, Paper1, physics) lol
@ZakiZaki-oo2rf Says:
You can easily understand this without making it overly complicated by splitting the motion into two parts:
Rotational motion: If the small circle stays in place while spinning, completing one track around the larger circle yields 3 full rotations.
Translational motion: Sliding the small circle along the outer perimeter without spinning adds 1 full turn due to the revolutionary path.
Summing both (3 + 1) gives the total result of 4 rotations.
@farber2 Says:
10:13 this does it for me.
@farber2 Says:
Ok, straight line 1 to 1, with a shape, add one circumference.
@jimsodowsky1298 Says:
I can totally believe it!
@tmeuschel71 Says:
I got this right and asked the teacher why the answer wasn’t on there. Then she said that you NEED to pick one so I wrote right next the score card the answer and choose the closest one to it.
@cenaalan5825 Says:
360 degree RELATIVE to what? Yes, there is 360 degree rotation, but RELATIVE TO OBSERVER (to you), however if we consider rotation from surface of second coin it did only 180 rotation. Because for flat inhabitant of second's coin surface, full rotation is defined when first coin's neck touches its surface again (not a head).
@cenaalan5825 Says:
From 3:28 to 3:33 mislead. Coin rotated only HALF of it's circumference RELATIVE to SECOND COING. However it did full rotation RELATIVE to side observer who watches on desk or computer desktop. If you would consider second coin as surface of some planet on surface of what you stand, you will never say that coin did full rotation on South pole, because full rotation for you mean that surface is touched not with a head but with a neck!
@consalvi9960 Says:
Now explain it like im 5
@Bnor6839 Says:
Ain't no way i solved it correctly (i also found 4 rotations) on the first try 😂. It was simpler than i had thought at first
@Sutta123 Says:
oh wow i got it right , when i tried to solve it i got 4 and i thought i made a mistake. the way i solved it is that i didn't look at the circle B but at the circle traced by the center of circle A and its radius is 4x ( where x is the radius of circle A and adding the radius of circle B (3x) gives the radius for that circle 4x) and therefore we get 4.
@readytodie-234 Says:
no answer in the option it is 4
@ShortsTo-Watch Says:
The mathematically correct answer is 4 and it is not an option in the choices.
Let radius of circle A is r. Then the radius of the circle B is
3r+r=4r
As A rolls about B, the center of A moves about a circle of radius
3r+r=4r.
So the center moves a distance
2 π ( 4 r ) = 8 π r .
One trip around circle A is the same distance as the length of its circumference,
2πr . Thus,
8πr 2πr =4 .
There is one extra rotation because circle A is spinning around circle B, in addition to the three rotations shown by the circumference of B. Therefore none of the given options is correct and the answer is 4.
@tomjones6777 Says:
Yup, my response was to calculate the circumstances of the two circles, convert them to linear measurements to determine that three was the answer. But I did learn the approach and individual’s frame of reference impacts the answer or answers.
@Ridham199 Says:
My teacher will still not accept this 9:02
@ahaf1605 Says:
Now I realize I'm dumb at matematics. hahaha. I thought I was good enough
@Harry-c5h2n Says:
I guessed 9/2 aka 4.5 close enough ;)
@skiguy87 Says:
The perception part that you said, I just want to add one thing here… when we see the small circle moving around the bigger one and come to the first position where ‘A’ written on smaller one is in original position, we consider that the smaller circle has rotated itself completely around the bigger one.
Now here is the catch, other then perspective of the bigger circle, we can also say, that the initial point of contact of smaller circle, when repeat itself, that point where it is repeating, will be taken as the point where the smaller one has made the full rotation of itself.
When we see the “A” coming to its original state after rotating (covering about a quarter of length), we are intuitively considering it as its first rotation, thus ignoring the explanation of point of contact as above, which it is doing it when its covering an additional quarter distance…
So what we have to monitor throughout the move is the Point of Contact and not the Orientation of the Rotating Coin or body.
@Tachyon836 Says:
I took the ACT lol
@HenriqueFernandes-c1u Says:
the typa shi bro sends me after he get 1000 on the SAT
@johnbrand9179 Says:
Just give those taking the test, a compass to draw a 3 to 1 ratio with 2 circles.
@Silvio-gk Says:
Anyone remember the sound effect at the start of a video of veritasium?
@SANDIPSAHA-x8u Says:
its wrong
@SANDIPSAHA-x8u Says:
the video started i saw the question it came out to be 3 now to see if i was correct
@lincolntowns1480 Says:
Technically they stopped using the SAT after Covid, but that has nothing to do with the actual reason. They stopped using the SAT because it was deemed “white supremacy” and racist
@ripcisco Says:
am i dumb or is this the only good thing to watch in 2026!😮😂
@herwincalinawan Says:
I was right, without the choices my first answer was 4. But when the choices was presented, Im confused.
@socialsheen91 Says:
3:28 i think this is wrong. Coz the rotating coin's contact to the main coin is the bottom part, so the rotation should finish when the rotating coin touched the starting point. So technically 3 is correct. For the example of the more accurate scale, the starting contact point is on the right side of the coin so the rotation should finish when it touched the same contact point, but he counted when the A is upright and not when the starting contact was fully rotated.
@user-ql3li8ov2o Says:
Very nice idea back your video
@PESARO-URBINO-x5g Says:
è lo stesso principio per cui il giorno solare e il giorno sidereo hanno durata diversa
@coindrop Says:
When i looked at the 2 circles in the beginning of the video I tried rolling A around B in my head and 4 definitely seemed like the right answer at least visually.
@indianajohn5669 Says:
Very badly worded question.
"Rotation is the spinning of an object around its own internal axis"
The answer is 3.
"Revolution is the orbital
movement of an object around an external center or body."
So, the answer is 1.
The N+1 seems to be something different.
@kbidata Says:
Duuuuuuude.
@Lego6980 Says:
That was really interesting- especially the application to astronomy. 🙏🏻
@kristinessTX Says:
My answer was 4 before you showed us. I graduated high school in 1993 and I took the ACT test scored in the 98 percentile for spatial relations and intuitively. I recognized that the coin would do a full rotation each quarter based on a size difference… How I knew that I don’t know I just know it. I guess I guessed 4 because a was 1/2 the size of B. So I knew I would spend four times based on radius of each circle. I interpreted the question to ask how many times did a spin around me? Is it a complete circle around B? But bottom line this question is terrible.
@jeremybeets2430 Says:
The SAT question should not have been changed, because they were only asking how many times the smaller circle would have to spin to travel around the bigger circle. So the correct answer is 3 the extra spin is not real. If you hold an object in your hand a turn completely around and hold the object still in your hand as you turn then this perspective spin will happen automatically. So that is not the smaller circle spinning that is the room spinning around the smaller circle but it has nothing to do with getting it around the bigger circle, and that was what the question was asking.
@RoastToast77 Says:
Me who used rotational physics and got answer 4 but seeing option changed my mind thought i was wrong
EDIT: i just used outer circle would revolve about center of big circle thus no. of revolutions = 2π(R+H)/2πR
@mikebell4649 Says:
Not noticing that the paper only says what law school “he”can go to not they can go to.
@juliotancredi7468 Says:
I think the question is not worded very well. It should be:
In the figure, the two circles are tangent to each other. Let's call the current point of tangency of the smaller circle P.
How many times does P become a point of tangency with the larger circle before returning to the position shown in the figure?
The initial point of tangency is not counted.
The answer is 3.
@aaronmichellejones2127 Says:
It was F
@Spiceyyt-o1b Says:
meanwhile JEE advanced s
tudents laughing in the corner
@MauroGames_ofc Says:
IT ROLLS 2 TIMES, THE COIS GETS THE ARROW DOWN 2 TIMES Aaaa 🤯
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