2022 AP Physics 2 Free Response #3

Walkthrough of the 2022 AP Physics 1 FRQ #3

Link to the released FRQs:

Link to my PDF Solutions:

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[AllenTsaoSTEMCoach]

Corrections:

part(c): My boxed answer for part (b) was correct, but I accidentally squared r instead of q when simplifying for part (c). The relationship is right, but the equation should read -1/2 k qe^2/r

[alphacenticle]

For total energy I added the electric potential energy instead of subtracting. If I did all other things will I get partial credit

[khaleelcheats]

Hello there. I like your work. Which program do you use for the annotations as you present the video?

[alexproshkin]

I didn't put rest mass energy for the total energy question, but put potential energy and kinetic energy so I got the same answer as you without the + me * c^2. How many points will I lose do you think?

[alexproshkin]

Would I lose points for using k instead of 1/4*pi*epsilon?

[vashXIII]

On part d.iii for the graph, would the kinetic energy on the new graph have to be equal to half the new potential energy no matter how long you draw the potential energy bar? When simplifying the equation for the total energy (ignoring rest energy for simplicity) you get KE - PE = [ ke^2 / 2r ] - [ ke^2 / r ] which shows the kinetic energy to be half the potential energy. That relationship shouldn't change after absorbing a photon.

Not asking about rubric points, asking as a teacher trying to solidify understanding.

[kingbi]

For the total energy question, I forgot to include the potential energy, so I know I lost that point for sure. But later when it asked it was consistent, I said it was not, since I didn’t include the potential energy. But my equation is indeed inconsistent, would I still get the point for the right reasoning but the wrong derivation?

[alexproshkin]

I think you have a mistake in part B and subsequently in part C. On the right hand side of the final equation for B, you simplify the electric potential and kinetic energies to -1/2 k qe / r^2 instead of - 1/2 k qe^2 / r. The same equation is then used again for part C.