I want to teach "measurement" to grade schoolers

[lightgrav]

coat-hanger balance can slide quickly into an UN-equal arm balance.
This carries implications for directionality (including negatives!), torque sums, and mass moment (c.o.m.)
students need to have negatives on their number-line around multiplication ... before they start division.

 

[vela]

Error analysis would have to be simplified to teach 8-9 year old students but taking very simple problems would be very important to promote critical thinking about accuracy. I am well aware of the errors I have made in the past relying on sampling periods that were too short or long or out of phase. Thanks for the reminder.

In my astronomy lab course, I'll be dealing with college students, but I don't see why 8 to 9 year olds couldn't do these activities as well. I'm planning to have students take measurements using a cross-staff and quadrant. The cross-staff is made out of card stock and a yardstick or meter stick. The quadrant is made out of card stock, a pencil, thread, and a small weight, like a small washer, nut, or key. They're easy and inexpensive to make. The students typically see a range of measurements when making angular measurements using these instruments, unlike using a ruler to measure length where getting the same result from repeated measurements is common.

Students will have to try explain why they don't get the exact same measurement every time and to identify the possible sources of the variations. Next, I'll going to have them plot their measurements on a number line so they can visually see how the data are spread out. They'll need to figure out how to estimate the true value from their data and to (numerically) describe how spread out the data are. With any luck, some groups will have data with varying amounts of random error, and I can then ask the students which results they'd trust more and why.

 

[lightgrav]

I recommend plastic rulers that can attach/detach from the end of a 57 cm (long) dowel ... then, the cm marks are degrees.
You can usually find plastic protractors for ~ $4/dozen, and they last for years;
a straightened paperclip hooked into the center-hole hangs vertical even in a breeze, and can be easily held by thumb to "lock" a sighting.