I have been looking the internet far and wide for an explanation of why the slope changes at v=0 for part e of that first free response and still can't find it. Friction would be present when the block is on the way up or on the way down, so why would the slope change when velocity goes from negative to positive?
You're a life saver, thank you so much for doing this! In question 3, when asked to find the final velocity of the rod, I solved for the angular acceleration using the torque on the rod. I then used the rotational kinematics equations to solve for w and finally use v=wr to solve for v. I ended up with sqrt( 3pi g /2L). Why is this method wrong? What am i missing
As the rod pivots, the torque is changing (the force is straight down, but the angle is changing). Conservation of energy will likely prove MUCH simpler!
In part a(i) of FRQ #1... the problem says it is a time t after the block was projected up the ramp. Why is gsin(theta) positive instead of negative? Especially since the acceration vector is in the same direction the whole time.
It all depends on what directions I chose as my positive x- and positive y- to begin the problem. Once I choose those, I stick with them for the duration of the problem.
@@DanFullerton Hi, so when actually answering these types of questions, I can adopt a different direction as positive? The Scoring guidelines didn't offer another scenario, only about when going downwards is designated as positive.
for #1 part D, wouldnt the frictional force be equivalent to mew (however you say frictional coeff.) times mg times cos of theta since this is on a plane? Therefore, it would look something like (coeff)(mgcostheta)
You are right, I misread / misheard the question somehow. Thanks for doing these! really helps since my physics teacher sucks at teaching (Although I still respect her since she is trying). She literally said "Sorry, I can't continue teaching because I don't know this material enough" 5 times throughout the year, so I relied on your videos for help
Hm... Bc the way I'm thinking is that you would have to overcome a larger force to get to that position when v=0, so it would take longer. What am I missing?
Of course the AP 1 FRQ I had was a completely different version than the one posted on college board so I'll never know the correct answers to the problems.....thanks college board
thank you! way more helpful than my AP physics teacher is!
I have been looking the internet far and wide for an explanation of why the slope changes at v=0 for part e of that first free response and still can't find it. Friction would be present when the block is on the way up or on the way down, so why would the slope change when velocity goes from negative to positive?
You're a life saver, thank you so much for doing this! In question 3, when asked to find the final velocity of the rod, I solved for the angular acceleration using the torque on the rod. I then used the rotational kinematics equations to solve for w and finally use v=wr to solve for v. I ended up with sqrt( 3pi g /2L). Why is this method wrong? What am i missing
As the rod pivots, the torque is changing (the force is straight down, but the angle is changing). Conservation of energy will likely prove MUCH simpler!
Hi!
For #1 Part B, will xmin not be D minus the displacement? And since the displacement is negative, it should become positive right?
Vyom Raval Also for #1 Part D, should it not be negative Vo^2/2(coeff)(g) since Vf is 0 and Vi is Vo and its Vf^2-Vo^2?
Can you please post AP Physics C 2016 Mechanics FRQ solution? Questions were released today
how does the energy of the top equal the energy of the total? at around 16:00 thank you!!
In part a(i) of FRQ #1... the problem says it is a time t after the block was projected up the ramp. Why is gsin(theta) positive instead of negative? Especially since the acceration vector is in the same direction the whole time.
It all depends on what directions I chose as my positive x- and positive y- to begin the problem. Once I choose those, I stick with them for the duration of the problem.
@@DanFullerton Hi, so when actually answering these types of questions, I can adopt a different direction as positive? The Scoring guidelines didn't offer another scenario, only about when going downwards is designated as positive.
for #1 part D, wouldnt the frictional force be equivalent to mew (however you say frictional coeff.) times mg times cos of theta since this is on a plane?
Therefore, it would look something like (coeff)(mgcostheta)
Desertdouuche Not in this case, since the question states that the friction occurs on the horizontal surface, not the plane.
You are right, I misread / misheard the question somehow. Thanks for doing these! really helps since my physics teacher sucks at teaching (Although I still respect her since she is trying). She literally said "Sorry, I can't continue teaching because I don't know this material enough" 5 times throughout the year, so I relied on your videos for help
In 1d, if you have friction pushing in the opposite direction as the velocity, wouldn't you hit 0 velocity after Tf/2?
planetpeter917 Nope, you'll hit it before tf/2.
Hm... Bc the way I'm thinking is that you would have to overcome a larger force to get to that position when v=0, so it would take longer. What am I missing?
Ohhhh wait shoot never mind solved it with fbd
Can you please do AP PHYSICS 1 and AP PHYSICS 2? thanks
Tyson Van They are in process, I hope to have them complete by the end of next weekend.
Of course the AP 1 FRQ I had was a completely different version than the one posted on college board so I'll never know the correct answers to the problems.....thanks college board
Dan Fullerton AP Physics 1 is up. AP 2 may take me a few more days to get the video processed.
Hi,
How many points do you think id lose if I forgot the "D-"
Classius Clapeyron Hard to say, but I doubt it would be a significant amount.
This video has been a great help. 10/10!
Hi at 4:51 why did u add D
D is "x naught". It starts at a position of "D" away from the top.
Thanks a lot, this was sooooooo helpful
+Spencer Zezulka You are very welcome!
For the last one, could you say to use heavier rods since that decreases friction I think?
ap exam tomorrow wish me luck
Best of luck!