Metric Mastery B

[JustDroobles]

This event bothers me for several reasons. It's not just the density thing. How about temperature? How can a supervisor hold something at constant temperature (scoring correctly requires this) for the duration of the event without an expensive temperature-regulated water bath normally found in a laboratory? I'm hesitant to asssume that even water won't have fluctuations in temperature over a few hours. It would equilibrate at room temperature (within what margin?), so I suppose an 'actual' temperature could be recorded before the event is ran or something (that's not good practice). Is that the best that can be done? That is a bit lame considering estimating room temperature is one of the simplest possible tasks.

Well complaining about the event here is not going to change that fact that you need to learn how to measure and estimate temperature. All you can do is your best, and if it is unfair for you it is unfair for everyone, so you aren't necessarily at a disadvantage.

I ran this event this weekend and I think my two temperature stations were successful. One was a beaker on a hot plate, which will keep it at a constant temperature. I checked before each session to be sure. I also asked for the room temperature in K. I checked the room temperature throughout the day and accepted answers between the minimum possible answer for the minimum and maximum possible answer for the maximum. All of the kids who appeared to know what Kelvin is were in the correct range. Otherwise, they were way off.

I also ran a successful density station. It was a simple cube and they were allowed to measure the mass with an electronic balance in order to complete the station in one minute.

[Skink]

I also ran this event this past weekend, so I am not entirely clueless. The issue is holding anything at a constant temperature for 2hrs+ is unrealistic, and, in order to have a tightly-ran event, that's almost a necessity. I went with ice, but that drifted even when insulated. Scoring according to the rules calls for a single supervisor-measured 'correct value' and does not take into consideration drift over the course of the day. I can imagine it's even more exaggerated at larger State tournaments like in my state where there are three groups for every event.

I used a cube, as well. It was about the only thing I figured could be measured quickly enough. There is one other way to do it, and that is to provide one of the measurements (i.e. giving the volume and some way to measure mass or vice versa and asking for density in some units).

[billyhoho]

Is there any way to estimate mass without hefting? I mean, pretty much everything has a different mass and without volume and density or something, you're pretty much dead. Also, I'd think the only way to get the density right, quickly, would just be to memorize the density of random, everyday objects since I doubt people are going to bring in a box of diamond or a lamp or something.

[Skink]

Well...yes and no. If it's a common everyday object, then the expectation can be you should be able to ballpark it*. Anything else, the superisor should let you heft to get a feel for how massive it is. The reason is because, without knowing density, you could be deceived otherwise as to how much stuff is actually occupying a certain volume. Tricky supervisors can find objects either way too massive for how small they are or the opposite. I would imagine higher level competitions would be full of odd objects like those. In fact, some physical science college professors have objects crafted just for the purpose of being deceptively too massive for their size (or, again, the opposite) in order to teach density.

*how many tournaments have folks been to where the supervisors have not allowed manipulating objects during the estimation portion?

[cconry]

I'm new to this. It doesn't seem like you can have an estimated value for the last digit on a vernier caliper. I am right?

[PacificGoldenPlover]

The estimated digit on a caliper is the .01 mm digit.

[Skink]

If you want to see how it works, use it to measure something you know the dimensions of, like a coin or something, until you get the correct answer.

[dholdgreve]

I'm new to this. It doesn't seem like you can have an estimated value for the last digit on a vernier caliper. I am right?

That would depend on whether it is digital or mechanical.

[wlsguy]

I'm new to this. It doesn't seem like you can have an estimated value for the last digit on a vernier caliper. I am right?

You are correct. Because using a vernier caliper involves determining which of the "marks" is to be used for the final digit, it cannot be estimated. (unless you consider this the estimation).
See this website and the simulator for more info
http://www.physics.smu.edu/~scalise/apparatus/caliper/

[ali941]

Well...yes and no. If it's a common everyday object, then the expectation can be you should be able to ballpark it*. Anything else, the superisor should let you heft to get a feel for how massive it is. The reason is because, without knowing density, you could be deceived otherwise as to how much stuff is actually occupying a certain volume. Tricky supervisors can find objects either way too massive for how small they are or the opposite. I would imagine higher level competitions would be full of odd objects like those. In fact, some physical science college professors have objects crafted just for the purpose of being deceptively too massive for their size (or, again, the opposite) in order to teach density.

*how many tournaments have folks been to where the supervisors have not allowed manipulating objects during the estimation portion?

At the Bay Area Regionals, we were only allowed to touch the objects where we were estimating mass, density, and temperature. When they asked us to measure density, they either gave us the mass and we had to find the volume or vice versa. With temperature, one beaker was on a hot plate, and I believe the other was at room temperature.