I’m a fan of the University of Toronto physics department’s elevators.
…is it because they’re fast?
…do they telepathically know which floor you want before pressing a button?
…do they transport you by moving in more than one dimension?
Nope. Better. Let’s take a look inside…
Hmm… looks pretty standard so fa — but wait! What’s that in the far left corner? It looks like a glass cylinder. Let’s go in for a closer look…
<ghasp>It’s a force meter attached to a 750g weight!</ghasp>
A force meter is a type of measuring instrument that enables you to measure the amount of force acting on the object it is attached to — which in this case is a 750 gram weight.
If you don’t understand why this interesting, you need to understand the following: physicists like solving problems, and at least once in every physicist’s life (s)he wonders “what is the acceleration of this elevator, and what g-force am I experiencing?“. This question, of course, bothers us for the whole 30 second elevator ride, and we wish we had a measuring apparatus to figure it out. Eventually the curiosity subsides and we carry on with our daily lives… but now in the U of T physics department, we don’t have to.
Let me show you how it works. The top of the force meter is attached to the elevator and the bottom is attached to a hanging weight. The force meter will measure the force between the elevator and the weight. If the elevator is not accelerating (even if it is moving at a constant speed) the force between the elevator and the weight will be that of gravity. As the elevator speeds up to move to a higher floor it will have to pull on the weight with a greater force so that it not only counteracts gravity, but also pulls the weight upwards. Newton tells us that the net force acting on an object is its mass times its acceleration. So if we know the force acting on the weight and what its mass is, then we can find out the acceleration. I took a quick reading and noticed that the difference between the force when the elevator was not moving and when the elevator was accelerating upwards was approximately 1 Newton. So we can take this, divide it by 750 grams (using google calculator) and find that the result is an acceleration of: ~ 1.33 m / s2.
Great! Now let’s get some context on this. Comparing it to gravity (which is 9.81 m / s2) we can say that an elevator accelerating upwards is equal to a g-force of: 1.14, which is small considering that fighter pilots can withstand a g-force of 9. Taking the elevator downwards will initially give you a g-force of: 0.86, which is roughly comparable to standing on Venus (0.904).
So, yes… very awesome. It makes me wonder how many other universities’ physics departments have little things like this. What kinds of neat publicly accessible physics toys are in your physics department?
This is a pretty neat idea. I don’t think it would work in our elevators – mainly because they are as slow as plate tectonics. I tried to measure the acceleration with the PASCO force plate and it did not give very good results.
Also, did you have any problems with safety people claiming this was against fire code or something? I know it seems straight forward, but it must be these people’s job to make something of nothing. I know this would be a battle at my school (unless I just put it in there without asking anyone).
I don’t know of any bureaucratic troubles the physics department might have had… but there were some problems to do with the force meters being too popular. One person liked the force meters and weights so much they decided to take them without asking… presumably to preform further measurements on their elevators at home…