AP Physics 1: Algebra-Based (2015-2016)

@xybear FRQ 5: Ok I reread the problem and I now see that it’s a vertical string. I mentioned something in my response about longer wavelength so I’ll prolly get 3 ish points then.

For the equation/data. It just realistically can’t. Her data would start curving at 0 up to the initial data points. You have to force through the origin which her slope does not. Her +b value was like 1m/s. If you did any labs during physics. You are likely taught to 1. Get a linear slope and b) force it through the origin if it made sense (which it often did). And this is an example testing that experimental concept.

@lrylander 2c is asking you to violate a physical principle that can’t be violated. An easy choice is violating g (9.8 m/s) by making the ball have more kinetic energy on its Return than its original potential energy at the starting height.

@Dayruiner Why does the graph need to go through the origin? And yeah, it wasn’t perfectly linear, but approximately so (line of best fit).

The thing is they may not provide points for lack of simplification. At first I hesitated because they required the inclusion of ‘M’. But at the end, it says “if appropriate”, meaning these variables may not be necessary. Therefore, I am not sure as to whether they will take away points, but you do seem to have expressed a grasp upon using Newton’s Second Law, so perhaps full points will be given!

@Dayruiner If you would like, why don’t you discuss some Multiple Choice you had inquiries about or had trouble with

This may be a dumb question, but part C of question 2, the violation of a physics principle, would a data table showing the final velocity considerably less than the initial velocity and claiming this violates the law of conservation of momentum be a plausible answer to receive credit? In the response I explained that the ground or surface that the ball bounces off would gain some momentum, but I said it would not gain enough to conserve the momentum of the ball. Would this response be a plausible answer to receive credit?

Can someone explain all of question 3 with somewhat confidence? Including the graph

@Ahyeah #3:
(a) i & ii. The graph looks like a series of right triangles; velocity increases linearly, then drops at the bump. Vavg goes through the approximate middle.
(b) greater than; more space between the bumps gives the cart more time to accelerate and gain speed
© greater than; a larger angle makes the component of the gravitational force parallel to the motion (what is moving the cart) larger, so it accelerates faster
(d) i. The graph is consistent with her equation, both show direct proportionality between M and Vavg (if M increases, so does Vavg
(e) ii. No, the equation does not make physical sense for a few reasons; velocity is dependent on time which does not factor into the equation, Vavg /should/ increase with d but according to her equation it decreases when d increases.

@ohiobuckeye If the grading rubric assumes perfect elasticity, then yes, but in a realistic situation the ball would lose some energy/momentum and bounce back with less speed. A /more/ plausible answer would to make the final velocity a lot larger than the initial velocity, but I’m honestly not sure whether yours would be acceptable or not.

@xybear Thank You. That’s what I figured it would be sort of an unknown till I see the scoring rubric. Thank You

@xybear
Spoke with my physics teacher
For the graph. He drew a series of curves up and down (sort of like a sine) with v avg in the middle.
For car he said greater for both due to more distance and then more energy.
For the student he said the equation did not match the data because he said 1.5 m/s = 1 kg x constant. And 2 kg did not reach 3 m/s. and that it did not make physical sense due to mass having no physical impact on velocity because it cancels out in energy.

@xybear @Dayruiner okay sweet i said all of those!! However, for the graph, if you made the velocity after the bumps zero and then you made it linear (but after every bump the velocity started at zero), would you lose points??

Can someone provide answers for the circuit question?

@ahyeah
Probably because the bumps only slow it down. They don’t stop the car unless They wish to accept that it does. Again, odd questions they asked.

@Wheaties Current goes up in C. Down in A due to the parallel being broken so therefore C doesn’t split the current with B anymore and total R goes up making current in circuit go down for A.
Ranking was A=D>B=C due to A and D dropping the same voltage due to same resistance times current. B and C are same because Kirchoffs rule that parallel drop same Voltage. And they are less because it’s half the current for each R.

Is 55% a 4?

And will the curve be bigger this year (meaning a lower score needed to get a better score) because so many people failed last year?

@wheaties Probably. According to the College Board: Curves for first year exams are set by the council board for that exam. Each following year. The curve is based on the statistics of the previous year. So considering last year was a disaster. It is likely getting a 3 this year for students won’t be as hard.

For 3d, I put that the graph is not consistent with the equation because the equation implies a directly proportional relationship, so when mass doubles from 1 to 2, the velocity should have also doubled…

@lena33 I put something similar to that as well.

@Dayruiner where did you read that they were determined from the previous year? It looks to me they have a set % of each score that they keep consistent each year.