Phil Keller

I can’t disagree: we did this problem today!

Also, can I add that it is easy to write projectile problems that are way too hard, with challenging math but maybe not much more in physics understanding to be had.

I hope I don't "enforce" it either :) These are all style preferences, perhaps more useful for beginner problems. Still, I'd be curious to see an example of the kind of problem you are thinking of where the method is too constraining.

But I think I may see where you are coming from. Are you of the no-substitutions-until-all-algebra-is-finished school? If so, you are probably in the majority. I admit I am lax about that. So my students get away with solving for t and then substituting. That may be how we evade this issue

Well, okay. But the point is not to make doctrine but to encourage disciplined examination of each item. So given a launch speed of say 20 m/s at 30 degrees, I can ask: is that horizontal? No. Vertical? Still no. But it has components…

I make a chart that keeps horizontal and vertical separate but make a big deal that when either side of the chart hands you enough info to solve for time, you can “send that to the other side”. Is that what you are asking about?

We are not afraid!

Silly question: how are you measuring time? We started getting decent results when we switched to using phones. Now most groups are seeing errors of 5% or better. I can tell them that 30% is a measurement issue but say, 240% is a calculation error. Which mass spins? Which one hangs? 🤷‍♂️

“That’s seasonal” is apparently trader Joe fancy talk for “yeah we don’t have that”. Like calling it seasonal, giving false hope of eventual return will make things better. I see right through that…

If you are new to using Desmos, I have some brief intro videos here:

www.youtube.com/@digitalsatg...

Silly to take the SAT without these skills…

In case any of you work with SAT students, here’s a quick heads up: starting with the August test, the calculators that “do algebra” are no longer permitted. (So desmos fluency is even more important!). #Iteachmath

Agreed! But many textbook proofs use the binomial thm approach which has the same flaw. Btw, logarithmic differentiation gets it all in one swoop but it comes later in the curriculum. Good thing pedagogy can stray from the sequencing demanded by the proofs :)

Not saying it’s the best way, but I just realized you can show that the derivative of x^p =px^(p-1) for all positive integers p using the product rule and then induction. Just saying…#iteachmath

If the agreed convention is that .5 and greater rounds up, and if if we are interpreting “0.4999…” as a shorthand for the associated infinite sum, I think you have to round up. But it’s a fun question. It’s like, do you believe the math or not?

Things we need, things we don’t

Have they posted the answer key yet?

I think I have mastered the Dunning-krueger effect. AMA...

It’s one of the great things about Desmos (and also about Interactive Physics) that it enables this kind of authoring almost on the fly. It becomes part of your teaching vocabulary. This one really shows that one thing!

Well, it’s languishing for a reason. It’s expensive and not web based. Barely supported any more. But it really does many cool things better than anything else I have seen.

It’s Interactive Physics, an under appreciated, languishing software package that is actually quite amazing. (This is my second grandpa post of the day)

Teaching beats, played two notes together, 440 hz and 350 hz, then paused to explain what a dial tone is. #IteachPhysics and times change.

Yes, that’s how I saw it too. There’s an AP mechanics multiple choice question that asks you to choose the right graph. It looks like a parabola which would put the minimum midway between zero and the minimum necessary for rolling w/o slipping. But I think that’s not quite it.

I was totally nerd-sniped by this: A sphere is released from rest at the top of a ramp w angle theta. What value of mu will minimize the total mechanical energy it has at the bottom? I may have an answer that is reasonable and concise, at the end of messy work. #Iteachphysics

37 x 100 = 3700. Then 3700/4 = (3600 + 100)/4 = 900 + 25 so 925.

Nice idea!

Simple Harmonic Motion: real data and simulated! #Iteachphysis #capstone #InteractivePhysics

I was writing an SAT math problem and I goofed -- and created a more interesting (but still SAT level) question:

x - 3y = 4
y = ax + by

If the system above has no solutions when a = 5, find b.

#Iteachmath

I’m sorry to read this. I hope things get better. Anything we can do to help?

triple integrals in different orders

Changing the order of integration in 3d can be hard to visualize...#desmos 3d to the rescue! www.desmos.com/3d/kdggenuks7

#Iteachmath

This is incredibly helpful! Thank you for posting these. If it's ever in hard copy, I would be interested in a class set.