This Square Can Roll Like a Ball

hey everybody today i'm going to be showing you how you can roll squares basically i'll show you how to roll any shape with the right conditions so i bought this shape online after i seen a video of it rolling and i thought i have to have that when i got it and actually saw it i thought there's no way this can actually roll but suddenly i gave it a slight push and this is what happened there's also a different one a hexagon shape that you can also get to roll [Music] it's so weird it doesn't look like these should be rolling but they are so why would an object like this roll well it turns out that it's not that hard to roll things that aren't spheres you just have to provide the right conditions for example let's take this lego if i try to roll this lego i can't it may take a few tumbles but it's definitely not rolling but if i put it on a different surface then it rolls pretty easily in fact you could roll lots of things down the surface that aren't spherical but why so to understand why these non-spherical things can roll first you have to understand that in order for something to roll down a ramp there has to be some friction if there's no friction then the ball won't start rolling for example if i had this ball on a ramp and there were no friction it would just slide down like this it wouldn't start rolling but what happens in real life when there is friction is it rolls down the ramp and starts rolling and what the ball is doing when it's rolling is the point that's in contact with the ground has no relative velocity to the surface so basically any point that's touching the ground is completely stopped relative to the surface so that means that the linear velocity of the ball is equal to the rotational velocity times the radius of this sphere that's just another way of saying that the point that's in contact with the ground has to be completely stopped if it's rolling and not slipping so this is always the case in real life for example if i just throw the ball across the ground that's only slightly rotating then the velocity is greater than the rotational velocity times the radius so the point in contact with the ground is slipping across the ground so friction causes the velocity of the ball to slow down and the rotation of the ball to speed up until the point in contact with the ground is the same velocity as the ball and in the case where i throw a fast spinning ball at the ground when it hits the ground the rotational velocity times the radius is greater than the velocity of the ball so the friction on the ground will cause the ball to actually increase in velocity or speed up and slow down its rotation so i'm barely throwing the ball i'm basically just dropping it but because it's spinning the ball speeds up now this is pretty obvious this should happen but in these examples with the ball the time that it took to make the velocity equal the rotational velocity times the radius is dependent on the friction of the surface and the ball so a bowling ball in a bowling lane is spinning very fast but it only slightly changes its velocity or direction by the time it gets to the end of the lane because the friction is so low in the bowling lane now the same thing applies with the lego rolling if it's going to roll then the friction at the point of rotation needs to be greater than the driving force so if i have low friction like this then the block just slides but if i have high friction then it's easy to make it roll when you push it but since the lego is non-spherical it drops a certain distance before the other edge hits so you have some rebound effects basically it turns like that hits and bounces up but if you get it rolling fast enough then the distance it drops before another edge hits is so small that there's low rebound effects and the lego doesn't bounce but it just rolls smoothly so the faster you rotate it the less it drops in between each edge hitting the ground so what this basically means is that with a lot of friction and rotational speed you can roll basically any shape pretty smoothly so for these shapes they basically just extended the square surfaces so that there's actually not a flat edge so the rolling is more smooth than a normal square would be and so there's less rebound effects and you don't lose your rolling energy due to the rebound so there's almost an elliptical pattern around it as opposed to a flat square pattern like the lego so it has to roll right in the center to get that smooth roll same with the hexagon and the hexagon is actually a little bit harder to roll because it has to get right in that center and the area is a little bit less hey everyone thanks for watching another episode of the action lab i hope you liked it if you did don't forget to subscribe and also hit the bell so you can be notified when my latest video comes out and check out the actionlab.com for the action lab experiment boxes and thanks for watching and i'll see you next time you

Channel: The Action Lab

Views: 857,272

Keywords: rolling, rolling physics, science of rolling, the action lab, shapes that shouldn't roll, rolling squares, rolling square

Id: eZM0WtB3UX8

Length: 5min 30sec (330 seconds)

Published: Sun Aug 30 2020