Is a Spinning Gyroscope Weightless?

hi folks Phil David I'll ski here of the Ithaca College Department of Physics they were sitting in this chair as an undergraduate student that I first found a compelling video which challenged my understanding of the physical world the videos is of the late Eric lately a former professor of heavy electrical engineering at Imperial College in London and in the video he shows a 40-pound wheel precessing like a top and while it does this he claims that it becomes light as a feather and he can lift it over his head with one hand with almost no effort the following is a short clip of the video and if you want to see the whole thing click on the link in the comments this is an experiment with a spinning wheel a rather large wheel 13 inches diameter mounted in a ball bearing on a shaft 3 feet long I am going to hold it like this and swing it in a circle and lift it with one hand but only when it's spinning first of all let me weigh it to show you just how heavy it is if I talk you'll see that lifting it is quite an effort it weighs about 40 pounds and I can't lift it any higher than that without a lot of strain so now we'll spin it up to two and a half thousand revs a minute which point it becomes a live thing so here goes 40 pounds of wheel as light as a feather this is not a conjuring trick this is a fact of science watch it again carefully the fight about the spinning wheel so far everyone has missed so I did what any scientist would do I went about developing an experiment to test what I had seen I didn't have a lifting apparatus lying around the lab that I could use to measure the weight of the gyroscope during the experiment so instead I built one in the epic ecology machine gem I'd like to point out a few the features first there are four sensors that I can suspend the gyroscope from in order to measure its weight this is important so that it's not a human claiming that it feels heavier or lighter second just like in the video I can lift the gyroscope during its precession using this cordless drill and third other than operating the drill this removes the human element from the experiment but we still want to be sure that we have an appropriate analog for this experiment now here you could see Eric lathe weigh standing with his huge gyroscopes now he's supporting with his hands instead of a human we want to use a mechanical lift and we're gonna be supporting the gyroscope with support strings and force sensors now we also don't want to be using such a large gyroscopes 40 pounds is a lot and we can do this on a much smaller scale so instead we're going to use a small laboratory gyroscope even though this setup looks different it's still going to be the same experience as in lathe weights video now the experiment itself is very simple I've already weighed the gyroscopes addressed to get a baseline now I'm gonna spin it up and I'm gonna weigh it at three different intervals now the gyroscope is almost up to speed I spin it using a small battery powered electric motor and I set the two force sensors to take continuous measurements from here on out this way I can run the experiment in stages without having to stop now I want to do in stages so that I can tell what factors if any are causing a change in the weight of the gyroscope so the first stage is very simple if the gyroscope with a spinning rotor but not processing this is to tell whether or not the spin of the rotor is causing the weight change for the second stage I want to weigh the gyroscope while it's processing to make it process I'm going to burn away the support string of the main body now you're going to see the gyroscope wobble a little bit but that's because it has to fall a short distance in order for precession to start the final stage of the experiment is to lift it the same way in Eric Lake Lake did in his video now all that's left to do is for me to run the experiment many times and then analyze all the data I collect so what happened well the experiment was a success but it didn't support lathe weights claims you could see the data here that I gathered from the four sensors the y-axis is the force that was measured and the x-axis is time now the first thing you'll notice is that the forces measured were negative now this is simply because the force sensors are designed to measure both pushes and pulls and the way they were built a pole registers as a negative force so if we look at the data the red line is sensor one and that was supporting the extension rod the green data sensor 2 was supporting the main body so you'll see around 12 seconds the force for sensor 2 goes to 0 now that makes sense because if we recall the experiment I burned away the supporting string for that sensor of course after that it's going to read 0 Newtons now I've included the bottom graph the sum of the two force sensors because that shows the total weight of the gyroscope at any of our three stages marked out here so if we examine the linear fit once we consider the uncertainty the slope is zero meaning the weight of the gyroscope didn't change at all throughout the experiment therefore we can conclude that Laith weights claim was just a myth thank you very much for watching you

Channel: Ithaca College Physics

Views: 374,658

Rating: 3.7539361 out of 5

Keywords: Laithwaite

Id: t34Gv39ypRo

Length: 6min 44sec (404 seconds)

Published: Tue Apr 15 2014