Labs, AP and Honors

Lab purposes are almost always to confirm some conclusion about physics we have reached based on observations and derivations, often expressed as an equation.

For example, for Archimedes' the purpose should have read something like: to confirm that FB = density of fluid x g x Volume of object submerged. We can confirm this by using the volume found from this equation to determine densities and find they are the same as the accepted values. Also to confirm that FB is the same as the rise in pressure(density of fluid x g x delta h) x area of beaker.

Conclusions must address purposes and if they were accomplished.
By the way, we did not use the apparent weight ( Mobject xg - FB) anywhere in this lab and those who brought it up in their reports were simply misquoting books without understanding what we did in the lab.

For the AP field plotting lab, many of you drew curve shapes you thought should be true with no regard for whether or not the values of V on your supposedly equi-potential curves were equal. This is the worst kind of misunderstanding. If you are going to make your conclusions fit your your preconceived notions and not the data, politics or sociology is for you, not physics.

Also on AP field labs; since V=E dot d where field is strongest V changes the most rapidly so if equipotential lines are say .5 V, apart they will be closest where E is greatest. E is greatest where the field lines concentrate ( the more line per area the stronger the field). So the field and equipotnetial lines are densest in the same region.

Electrostatics labs: protons don't move in solids, electrons move in conductors and semi conductors and a little on surfaces of insulators and between objects in contact.

For many labs many of you either think incoherently or can't be bothered to take the time to write coherently; either way it makes for bad lab reports. Please think carefully about both what the lab showed you and how you will write about it.

And finally: labs more than ten days late are zeroes from now on