It's About Time C

[Flavorflav]

In my region, we don't even get free lunch - just bagels and coffee. I also have never seen an event nullified. It has been discussed when a supervisor really screwed up, but it has always been decided that a flawed event is better than none, if the event has any validity at all.

[faraway]

About the suspensions...

Razors are a pretty good way to suspend your pendulum. And they're virtually frictionless. Virtually though... not 100 percent frictionless.

What exactly do you have to do to calculate the regression of the period?

[Jazzy09]

the event coordinators are the coaches for my area. all coaches are required to do an event

[L42]

Yeah, that's usually what happens at Invitationals.

[captbilly]

About the suspensions...

Razors are a pretty good way to suspend your pendulum. And they're virtually frictionless. Virtually though... not 100 percent frictionless.

What exactly do you have to do to calculate the regression of the period?

I guess you are assuming that everyone will be using pendulums. Keep in mind that even though your pivot point may be frictionless air is not. Why would you have to calculate anything for your pendulum, you can measure the period and any changes with amplitude. There will be differences from the ideal pendulum due to the fact that the pendulum arm is not zero mass, the mass at the end of the pendulum is not a single point, there will be friction on both the pivot and due to aerodynamic forces, as well as coriolis forces, and maybe even local changes in gravity and electromagnetic field (I really think the last two can be neglected altogether). You can attempt to calculate the first three "errors" but you won't need to because you can determine the true period of the pendulum empirically. Let the pendulum swing and measure the period. Record the data at both high and low swings to determine how the period varies over time (as the swing decreases). Classic pendulum mechanics tells us the period won't vary with amplitude but frictional forces will cause a real pendulum to have a different period as the amplitude changes. All you need to do is measure the actual period over time (with a constant starting amplitude).

Unfortunately for those of us who like to worry about splitting hairs, there is no way the event coordinators are going to be able to measure the accuracy of our timing devices to even 0.1 second accuracy. The response time of the competitors and the people timing the competitors (if your even is run that way) is going to overwhelm the accuracy of a really good pendulum.

[saturnian]

Unfortunately for those of us who like to worry about splitting hairs, there is no way the event coordinators are going to be able to measure the accuracy of our timing devices to even 0.1 second accuracy. The response time of the competitors and the people timing the competitors (if your even is run that way) is going to overwhelm the accuracy of a really good pendulum.

The way the event is run for us is as follows: The event supervosors simply have sound files which they play and the actual competitors have to "time" with their own devices and write down the time they think it is. The event supervisors then check the answers against the lengtb of the sound file.

[kmeister87]

Hi everyone!

My partner and I have considered several different approaches to clocks, and are refining a water clock for regionals (started out with sand, but it turned out to be a bit inconsistent-- the flow rate seemed to vary from day to day. We're not sure if it was because of changing conditions, contamination of the sand, or because of the intrinsic way in which sand flows-- it flows from the center for a while, and then the outsides collapse in... it could be the error was introduced there.)

Anyway, we discounted a pendulum for regionals because we thought it would be difficult to judge time from where the pendulum was in its period; the bob spends more time at the outsides than at the insides due to deceleration at the top of its swing. It seems from what people are saying that this isn't so much of a problem-- are you combating that by just having a short period?

Also, to answer a question as well as ask one: In terms of studying for the test, we're approaching it by reading and taking notes on the recommended book, then building the binder from there based on anything we think needs to be elaborated on. We'll probably also end up doing some googling to cover random stuff that the book didn't cover.

[L42]

What book is that?

[kmeister87]

Jespersen, Fitz-Randolph, Robb. "From Sundials to Atomic Clocks: Understanding Time and Frequency" 1999. It's on the nationals page for It's About Time.

[Jazzy09]

one of my team members just got that book today