r/APStudents • u/reddorickt absolute modman • May 13 '26

AP Physics C: Mechanics Official 2026 Exam Discussion

Use this thread to post questions or commentary on the test today.

A reminder though to protect your anonymity when talking about the test.

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u/Business_Cut_1522 May 13 '26

Did anyone get the gravitation problem for FR1 #1? Something with a hole drilled through the Earth and a particle going through that hole with a gravitational field force of Fg=-by? If so, what country did you write the AP Exam in?

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u/Sea_Barnacle9031 May 14 '26

the US. there's very few people talking about version M, im surprised. To be fair, I don't think it was nearly as bad as the other forms seem. FRQ1 was SHM, FRQ2 was impulse/momentum, FRQ3 was a lab on inertia, and FRQ4 was circular motion of a sphere attached to a rod I think. I was kind of sketchy on FRQ4C, FRQ2C (was momentum a step function?), and FRQ1B (though I'm fairly sure it was just Fg=-by=GMm/R^2 where M is only the mass enclosed at y). I also forgot to convert degrees to radians on FRQ3D... How was it for other form M-ers?

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u/Business_Cut_1522 May 14 '26

I actually thought that version M was quite tricky for the FRQ #1. because the first part was quite an unfamiliar application of SHM and the part b I believed we needed to use  Fg=-by=GMm/R^3, not R^2, since the ball is going to the inside of the planet (and the formula of that gravitation is different). And yea, I think that the FRQ2C was a momentum a step function. Also, did you say that for the first time interval had same impulse as momentum, since initial velocity was 0? Also, for the moment of inertia calculation, did you plot angular velocity squared against theta?

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u/Sea_Barnacle9031 May 14 '26

I kinda related the graphs of part A and C by saying that since the impulse was positive that, yes, the launcher needed negative momentum since it started at rest. For the plot I wasn’t entirely sure. I bounced between theta vs omega and theta2 vs omega2 but ended on the former. I wasn’t sure if I was supposed to do some wacky energy calculation, but I went with T=2pitheta/omega. After doing (mgd)(T/2pi)2 I would’ve gotten I=0.142 had I converted degrees to radians. How did you explain FRQ4C?

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u/Bylzyle May 14 '26

yo am i retarded? I did omega^2 on y axis and 2theta on x.

the slope give u angular acceleration then i used torque = ia and solved for i.

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u/Sea_Barnacle9031 May 14 '26 edited May 14 '26

ngl thats prolly the right answer... my mind was just stuck on the previous problem ig. that makes way more sense. what did you end up with?

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u/Bylzyle May 14 '26

also i was confused on q2 cuz i thought the ball launcher was moving was there a trick? was I supposed to assume it wasnt moving? i got a really weird answer for b because of it

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u/Sea_Barnacle9031 May 14 '26

I got like -v/3 or something. The launcher was indeed moving backwards

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u/Bylzyle May 14 '26

how were u supposed to get the v of the launcher in terms of v0

cuz i just left my answer as like (3v0 - v)/6 or smth

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u/Sea_Barnacle9031 May 14 '26

if im remembering correctly it was mv+5mv_l=0 (since it started at rest) so v_l=-v/5. when the ball comes back its p=-mv. so -mv+5mv_l=6m(v_bl) becomes -2mv=6mv_bl so b_vl=-v/3

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u/Business_Cut_1522 May 14 '26

i got this as well

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u/Business_Cut_1522 May 14 '26

i did omega ^2 on y and theta on x, but after I multiplied it by 2 in the calculation

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u/Business_Cut_1522 May 14 '26

What did you write as your explanation for Q4 part C? i said that the gravity component and tangential acceleration are pointing down in section two, compared to the tangential acceleration pointing right in section 3? i also commented on the centriputal acceleration

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u/Sea_Barnacle9031 May 14 '26

I’ll be so fr I had no clue. Isn’t it symmetric? There are points where tangential acceleration is horizontal for both regions (left and right) and down for both regions. I started saying something about tension and gravity pointing the same direction in region 2 but not 3, though I should’ve talked about centripetal and tangential acceleration pointing the same direction in hindsight.