Yea, greater mass means greater Vf of the block system, which my conservation of energy means greater height that it can rise to. Greater height means greater angle. In fact, check the 2008 practice exam, a problem that was almost identical to this was in that exam. Anyone completely solve problem one?
1:
a. i. a=gsin0
ii. v=gsin0t-v0
iii. x=0.5gsin0t^2-v0t+D
b. xmin.=D-(v0^2/2gsin0)
c. Position: quadratic with upward concavity; y intercept at x=D, horizontal tangent at x=xmin
Velocity: monotonically increasing line, with y intercept at v=-v0. v final = +v0
Acceleration: horizontal line at gsin0
d. distance sliding on horizontal floor before stopping, x, = (v0^2)/2ukg (uk=coefficient of kinetic friction)
e. skipped
Hello. I recently took the AP Physics C test, and the Mechanics portion was called “Form M”. I am a bit suspicious for two reasons:
- Everybody else in my school got form O.
- Form M had absolutely ZERO calculus on the entire test (mc, frq).
Does anybody know what the deal is? Could it be a misprint of a AP Physics 1 test? I could have sworn it said “AP Physics C: Mechanics” on the front cover. But the questions were very hard when compared to the Form O questions that were just released online.
Does anybody know what this means, and should I be worried about getting a different form? Please reply!
Thanks, I dont think you needed to include the D for position because you are starting at x=0 tho
@Kyuutoryuu thanks for posting your answers -
on A. ii. wouldn’t the equation be v=v0-gsin0t? Because the problem is asking for the equation after it has been projected up the ramp (while it is still moving up - against the acceleration due to gravity) shouldn’t the signs be reversed? As t increases, the velocity should not increase - until it reaches the top and then the negative velocity would appear. - Actually I just thought about this and sign convention you used matches the x coordinate. Oops.
Same answers for the rest of part a.
For part B - same answer
Part C -
position: same answer - I did included both things you mentioned
Velocity: Same, just reversed like part 1 ii -
acceleration: this is likely just sign convention but I had the acceleration change sign at the midpoint - at t=v0/gsin0, since it affects the velocity differently before and after this point. Not sure if that is right.
Part D - same answer
Part E - I also skipped 
For the #3, would it be incorrect to use integral calculus around the center of mass x=L/2 and then use the parallel axis theorem?
I think that would be fine, as long as you used integrals to derivve the I at the center of mass
@ClassicalCollege Your answers are all correct, but there may be a point or two taken off for your incorrect sign convention. The problem specified that “down the ramp” is positive, therefore acceleration always has to be positive, since net force is always positive/down the ramp (mgsin0 directed down the ramp is your net force). Also, acceleration never changes sign for parts a-d, as the same forces act on the block going up the ramp as down the ramp; still normal and mg.
for the distance graph it starts at D, goes to x min, and then back up to D.
Also, isn’t the definition of negative acceleration if it is in the opposite direction as velocity?
@schakrab - no, negative acceleration I believe just fits the sign convention based on how you define your coordinate system. If acceleration and velocity are opposite directions, the object will slow down; if they’re in the same direction, the object speeds up. However, you can definitely have a negative velocity and a positive acceleration which means that it will be traveling in the negative direction at a decreasing rate.
Oh yeah, for #2:
a. 8.66 m/s
b. 4.33 m
c. 1.44 m/s
d. around 24 degrees
e. 1.08 seconds
f. i. Increase (I put same on the actual test)
ii. same
Anyone agree with these?
I’ll be taking physics C mechanics the upcoming year. Any tips on the general class or on prep books or any other resources?
@tagi1998 I highly recommend the Princeton Review (prep book). And before the exam, a year from now, watch FlippingPhysics’s videos on youtube for a holistic review on AP Physics C Mechanics.
@tagi1998 Practice previous free response. College Board goes back to 1998 but if you look online you can find them all the way back from 1974 (I can pm you for the links)
Thank you both @Kyuutoryuu and @stoopidfoose for the advice! Could you me the links that would be great!
@tagi1998 - I would second @Kyuutoryuu 's recommendation for the Princeton Review prep. book. It’s incredibly helpful and gives problems that in my opinion at least are a step above the AP difficulty level. It gives a nice review of everything you need to know (and possibly a little more) for the AP test.
I also found going through past free responses to be really helpful. I personally did every free response set since 2007 or so to prepare for the AP.
As for the class, I’d just recommend to seek help from your teacher and peers when you need it even if you’re not typically used to asking for help. I think this is one of the first classes where I was actually challenged and know that to get through some of the problem sets, we all needed help from the teacher at one time or another. Don’t be afraid to seek this help when you need it.
What do you guys think the curve will be this year, around a 60 for a 5? Because it seemed slightly easier than the 2009 test which was 50 for a 5 but I’m pretty sure that doesn’t account for the -.25 they had per wrong answer.
09 was 50/90, adjusted for the 2011 change.
I think that our test’s frq’s were easier than the 09 ones but that our multiple choice questions were a little more challenging. I don’t think it’d go all the way to 60–that’s a pretty drastic change. I’m guessing around 52-55 for a 5.
Make up exam FRQs for E and M were a shaft… honestly got wrecked.
I took the late ap physics c mech test. It wasn’t too bad although the FRQ’s were harder then the released 2015frqs. I got Form A, i’m not sure if that is completely different from the other form that were on the original test day.