These 3 Questions Will Test Your Inner Physicist...
ฝัง
- เผยแพร่เมื่อ 25 ส.ค. 2023
- I have prepared 3 questions meant to test how good is your physical intuition and thinking skills. No advanced skills required. Anything you need to know you have most likely learned in the school already.
Best of luck :)
attributions:
Pexels:
Video by Yaroslav Shuraev: www.pexels.com/video/vehicle-...
Video by Pressmaster: www.pexels.com/video/a-man-of...
vector graphics:
freepik, vecteezy:
ground, metal stuff by macrovector freepik
grass landscape by jemastock on freepik
ship by brgfx freepik
truck image by freepik
forest landscape Designed by jemastock on freepik
Mountain landscape - designed by vectorpocket on freepik
Metal ball designed by Yuliya Pauliukevich on vecteezy
sound effects:
mixkit.co/
Please create more videos similar to this one. I enjoyed this video very much.
Thank you, I will :)
I got them all right, which only means one thing: I've spent too much time on youtube:p
This was great fun, please make more videos like this one.
One question you could try out is: If you are at 45 degrees north (on earth), at an equinox, and you put a compass (or any object which can allows you to measure degress) on a table, will the sun move 15 degrees, or more, or less, each hour? (Don't look directly at the sun:p Use something which creates a shadow)
That's exactly the sort of question I think about before sleeping... Love it! thanks!
(I did better than you) :)
😣😣😣
which ones you got correct? :D
@@lukasrafajpps I was correct for the first two, I'm still thinking about the third, it's disturbing
@@physiquedebase7606it doesn’t seem disturbing to me but hey that’s just your own interpretation and i respect it
Yoo this video is actually really well done. I actually got surprised when I saw just how little is the amount of likes it has. Underrated content fr, I enjoyed solving the problems a lot. Hope you do another of these :D
thanks for the kind words :)
It's funny how I'm mindblown by your relativity videos and your reasoning capabilities and then... with a background in aerospace these problems are extremely easy to me, I feel smart LOL
I did get the first two correct with the same reasoning you explained, but not as detailed. I had no idea how to approach the third. I didn't think of the wheels having angular momentum. And I couldn't figure out if the car would accelerate relative to the truck due to the car engine maintaing the same rpm (which translates to linear distance per time).
Im not sure why on the last question the car crashing is wrong. Depending on the length of the truck and the car initial velocity those "pushes" can very well bring the car to crash into the truck. Not to mention, the increased linear momentum can't just disappear once the car is on the truck. Even without the engine on, the wheels would not lose all their angular momentum anyway.
I think the problem is that the options are badly posed. Car crashing in the track does not necessarily mean that the velocities add up.
Hi, yes you are right there is however a little problem to phrase it properly and simply at the same time. However, I wanted the viewer to realize that two options are certainly wrong (although you still might crush into the truck, your velocities would not add up) nor would your velocity remain completely the same. So only one option is a real possibility.
My first answer for the falling balls was the small ball for the same reason you describe.
For the second I also got it right for the right reason.
For the third, I couldn't understand the question (and I still don't think it's posed properly), because the answer depends on how much force is maintained by the engine on the wheels. If the velocity of the car is measured by the.dashboard dial, then both velocities will obviously add up. Yet if the wheels are turning freely without and engine applying force to them, then it's very likely that the friction from the wheels plus the upwards slope to get on the truck will simply prevent the car from getting on the truck.
So I really think that there's a very flawed assumption in the question: what car velocity are we talking about? Are the wheels free? If the wheels are not free and engaged by the engine, what does it mean to "maintain the car velocity"?
EDIT: IMO, you should reframe the last question this way:
- use a conveyor belt (like airport moving corridor thing) on the same level as the road, instead of a truck, to avoid confusing the issue with the problem of gravity to get onto the truck.
- specify that we ignore dissipative friction in the wheels/engine etc., and we consider grip with the surface that we assume to be 100% (no slip)
- clarify that the car's engine is not running anymore and the wheels are free. Or better, use a bicycle instead of a car to avoid this problem.
If you apply all these assumptions and still remain in the case of the truck, then the car will crash into the truck cabin if brakes are not applied, since the angular momentum transfer from the wheels plus the initial velocity of the car that is bigger than the truck (/conveyor belt) will result in the end in a positive velocity of the car/bicyle relative to the truck/conveyor belt.
nah bro I got called lazy twice and got em all wrong 💀
thanks for sharing :)
Requires humility to admit you got them wrong. ggs my G
i need more questions -- the first question was spoiled for me because my undergrad in chemical engineering covered dimensionless numbers in fluid mechanics; the second question was spoiled for me because i just watched a youtube video on the topic that actually carried out the experiment; and the third question is, as you say, pretty intuitive
great video, subscribed
ah, hopefully next time I bring something new to you :) thanks!
Answered first one correctly but struggle to explain it in a general relativity frame, where there's no such thing as a ''weight'' force
Exellent work! You got me once time :D.
so 2 out of 3 ? :D
Yes :)@@lukasrafajpps
I got the first and third right.
For the second I thought the water level would stay the same.
I guess I considered that the objects on the ship would cause it to displace more volume, equal to the volume of the objects themselves.
But since the extra amount displaced would be tied to the mass of the objects instead of their volume, it seems a bit silly to think that now.
For the first, I thought: obviously, the big one first, otherwise, I can make the small one as small as a grain of sand and it can't be as quick as a 1T ball for example.
But then, for the detailed explanation, I thought about dividing both balls into small vertical columns, with the same base area, but they will necessarily have different heights, so they would push air with a higher force.
I've answered all three correctly :) There exists a nice question, related to the first problem: We know that one liter of human body produces more heat (energy) than one liter of Sun substance. So, why Sun is so hot, while human body is not?
Well, I had a 1 in 9 chance of getting them all right and I guess it was my lucky day! Thanks for the quiz.
I am glad you enjoyed :)
I came back here after your video on the twin paradox. I thought about the first question again when you mentioned the equivalence principle. Let me start by saying I know I'm wrong but I don't know why. So if you start accelerating your rocket past the two balls in space you should see them remain at the same "level". But by your logic in the first question, if it was not an accelerating rocket and it was a uniform gravitational field, then would the balls not act like the did in the first question with the bigger ball seeming to accelerate faster behind you than the small ball? That seems like a way to break the equivalence principle to me.
By the way, I can't wait for you to make me look like an idiot, don't hold back.
huh? not sure what you are talking about. so i could be way off.
but first question is a fancy way of basically saying the same as the moon experiment of hammer and feather.
he's basically saying the smaller ball on earth, has bigger air resistance due to greater surface area relative to mass.
at least that's what i understood it as. but I'm no expert.
I got 2 out of three correct. The boat one, I got it wrong. Once you explained, it became obvious why I was wrong.
Fun video by the way. Thank you.
The third problem does not take into account that the car needs to climb up the ramp, loosing velocity due to that.
yea there is a probably lot of variables that should be mentioned in the third problem but all of them lead to the same answer. The car can lose a part of the original velocity during the climb but it still gets the push due to the transfer of angular momenta.
Got 2 answers correct, them being the first 2 but yes, I got lazy on the third one and assumed the answer to be the second option, considering only the concepts of relative motion.
As you said in the beginning, not much advanced knowledge was needed for these questions, which lowered my guard and hence didn't think of conservation of angular momentum. I guess for you it isn't an advance concept xD
The third question could have been a little well defined.
Overall a good and engaging video👍
Yes I agree that the third one can be a tricky but in all realistic scenarios the answer is the same. It is problem with physics that there is always a lot of things that influence your result but the important thing is how you think about the problem and whether you know how they influence the outcome. I also forgot about the angular momentum :)
@@lukasrafajpps Yes! Thats the beauty of physics. Cheers mate :)
The picture for the boat is wrong though. The level of the water falls down, but the boat must rise relative to the water. It doesn't in the animation.
EDIT: well it sort of does in the explanation section :)
I have an objection to your answer to the first question. Experimental results suggest that air resistance is proportional to the square of the velocity. If so, the effect of air drag could eventually take over to offset the gravitational force
but that doesn't mean the smaller object will overtake the bigger one. This effect apply to both with the same proportionality and therefore you don't need to consider it.
11:42 ❤
got all 3 wrong. Guess I'm not a physicist 😅
although my understanding of the 3rd one was that the difference in speed between the truck and car would cause the car to speed up a little.
like how if you grabbed hold of a car moving faster than you, you would get dragged along. like those old buses with open ends at the back.
1 the same time. But the big ball will fall slightly first due to smaller surface area to mass ratio .
2 remains the same .
3 The car gets a small push .
The momentum from the car is still added to the truck , causing the truck to speed up and car to slow down.
the truck will actually lose some velocity since the angular momentum of the wheels will be transfered partly to the linear momentum of the car and breaking of the truck as the wheel are basically pushing the truck backwards
@@lukasrafajpps question 2 I used the principle of floating objects on accident 😅.
The car is parking on the truck , so It needs to brake, so overall the truck gains momentum. What ever it took from the truck it will give back , plus what it had before parking on the truck.
@@m.c.4674 yea that is true but depends on the truck and car mass ratio. Yea if the objects were floating it would be different answer :)
I got only right 3rd, but just only I tried once, but I could not explain why this is correct answer. I got correct (partly) 1st but only by my mistake. I forget about air resistance, just follow free fall (Armstrong'height
Yea 3rd is kinda intuitive although most pepole (including me) forget about the angular momentum hidden in the wheels :). If there was no air resistance, the balls would fall at the same time no?
@@lukasrafajpps IMHO if bottom of balls are in the same height then yes, but if their center, I guess larger hit first,,,
Are you assuming that gravity is a force? Because it's not. We have definitely gotten that one wrong. Even Einstein said so. We really need to stop thinking of it as a force.
I didn’t get the third one… the car is moving! The engine is working. When on the truck, the car must start accelerating because now it has a new surface! Did I miss the part that the engine will be turned off right at the beginning of the experiment?
Hi, good point. In real world scenario since the car is maintaining a constant velocity its engine is working at a certain level. If you want to cosider the option A then the car would have to rapidly increase its power output to accelerate by such amount in such a small space not to mention the limited friction beteen the wheels and the truck. but it should be probably added to the question thanks.
_"The engine is working"_ - the problem assumes the car has a higher velocity than the truck to begin with, and the engine is in neutral (the car is just rolling) .
@@renedekker9806 Well, in that case, you also have to ignore the friction of the wheels and the gravity to get onto the truck... too many things not dealt with in the question. It should have at least posed it using a conveyor belt on the same level as the car, instead of a truck.
Even if the air resistance hadn't affected the balls, the larger ball would reach the ground first, because the centers begin at the same height, and the larger ball starts out nearer to the ground than the small ball.
correct, but I wouldnt count it as a correct explanation :)
Your 3rd question did not give enough clues. From this limited info, one could have assumed that both the truck and car drivers were instructed to maintain their speeds no matter what, in which case it becomes like the belt driven walkways at airports.
yes but not realistic. you would need infinite friction between the wheels and the truck and an infinitely powerful engine to maintain the same velocity relative to the truck since it would have to accelerate instantaneously
@lukasrafajpps You know what I am referring to by "belt driven walkways at the airports"? They are like escalators but flat on level ground. If you step on it, you will move along with the belt to the other end.
The belt is moving at constant speed. I can decide to run into the belt and maintain my running speed. I would need some adjusting and balancing, but this does not require any infinite effort as you mentioned.
I know what it is but it is not the same. The difference is in how human body moves and how car moves. We use almost the same amount of energy to start moving as when we are moving. Our bodies move very ineficiently. Therefore it is not a problem to quickly accelerate to the speed of the walkway. This is not the case in the case of the car since it takes much longer to accelerate to a reasonable velocity. The biggest difference however is between using legs for moving and using wheels for moving.
@lukasrafajpps I truly appreciate your feedback on my replies. You said that the movement of human legs differs from that of a car. I still disagree. I can push a cart on 4 wheels onto the moving belt and still achieve the same result. In this scenario, the cart is the equivalence of the car, and the moving belt is the truck in your problem. Me pushing the car should be considered as the equivalence of the engine of the car.
@@caperider1160 no, your wheels would start spinning but car would move barely
My lazy brain got the second one wrong 😁
:D still beter than me
Fck this all wrong.. 😢. I would swear the smaller ball will fall first😅
I just found another question that you might add to your repertoire. At least the explanation appears to be correct. th-cam.com/video/AL2Chc6p_Kk/w-d-xo.htmlfeature=shared