2015 #1 Free Response Question - AP Physics 1 - Exam Solution

This Short Answer question also works as a part of the AP Physics C: Mechanics curriculum.

0:00 Intro
0:11 The initial setup
0:29 Part (a)
1:52 Advice about Free Body Diagrams (or Force Diagrams)
2:47 Part (b)
4:37 Part (c)
6:34 A shorter answer to Part (c)

Next Video:
Free Response Question #2 - AP Physics 1 - 2015 Exam Solutions

AP Physics 1 Review Videos

Multilingual? Please help translate Flipping Physics videos!
- 本Flipping Physics视频已有中文字幕。谢谢Junjiang Li!

#APPhysics1 #ShortAnswer #Forces

AP® is a registered trademark of the College Board, which was not involved in the production of, and does not endorse, this product.

[iArtificialMoron]

I've learned more in watching a few of your videos than I have in almost the entire school year. The explanations are straight forward and I have an easy time understanding. Thank you so much!!!

[FlippingPhysics]

Would the awesome person who just did the Chinese subtitle translation for this video please let me know who they are so I can thank them properly?

[sherryyang]

The test is tomorrow!! Thanks for the series of ap physics 1 videos. They are all very helpful. You deserve more views!!

[ashleyfong]

YOU HAVE THE BEST EXPLANATIONS OUT THERE. all those other videos leave me confused, but your explanations are so clear, and entertaining. THANK YOU SO MUCH. this helps immensely. pressed the thumbs up button.

[josephrao]

Thanks so much for the great videos. I'm going to give these questions to my students and I always think seeing someone else go through them is good for both my students and myself. Seriously love what you do!

[Abstract.x]

You are amazing, came to this channel pretty late but I appreciate how much work you put in every video.

[ashleyfong]

hey to all those ap physics 1 testers tomorrow (including myself)- you all got this (: dont forget to take a deep breath, and dont stay up too late cramming- get a good nights sleep!! :)

[jonesjones]

The AP Exam is tomorrow and this did wonders to ease my nerves as I do some last minute reviewing. Many Thanks!!!

[funshorts]

I really appreciate your all videos. They are all amazing as you explain everything visually. Thank you so much for your help.

[noahie]

holy crap this was one of the most helpful videos i've ever seen

[uah]

*I don't understand this thing from AP Physics 1 2017 FRQs Q#3. I'd be thankful to anyone who could help me out with this.*
My reasoning about Q 3 part (a) was that the disk should hit the rod at the *left* of point C because the moment of inertia is inversely proportional the angular speed from the momentum equation.
So if the mass is more spread out from the pivot (when it hits a point left of C and thus farther away from the pivot), the moment of Inertia increases ( I=mr^2) and thus the angular speed decreases. (Due to Law of conservation of angular momentum.)
We have used this same reasoning when we talked about a girl moving her arms in versus moving her arms out while rotating as she changes her rotational inertia and thus her rotational speed. That's where I got the idea to do this question this way.
According to the Scoring Guidelines, this is clearly wrong and they don't even talk about anything like this and focus instead on torque.

In Q 3 e, can I say that had the disk been stuck to the rod it would have had a larger rotational Inertia and thus a smaller angular velocity. When it bounces off, it has a greater angular velocity compared to sticking to the rod as now it has a smaller inertia. Please tell me whether this is correct or not?

In this question they also mention that the mass of the disk should be considered much smaller than the mass of the rod and then for the later parts we shouldn't assume this.
I want to ask what is the significance of this assumption. Why does this thing matter?

[feyzayucel]

This problem was in a frictionless and massless pulley and string scenario, but what if there were friction in the pulleys, and their masses weren't negligible? How would the problem be solved then? We'd have to use rotational dynamic, right? But how would we do it?

[edwardv.]

Studying for this exam over Christmas break.  Currently pretty lost, but hopefully i'll understand better in May!

[YacineBenkirane]

AP Physics Exam in a few days. Thank you for the detailed derivations.

[billwindsor]

Awesome job on your AP Physics review videos, *thank you!*

[bt]

Thanks for deriving the question part C for me because it helps alot

[danielkwon]

In AP Physics C Mech 2012 Relased test, one of the answer said that Tension on the block was greater at Block 2
(in 2012, there were no two wheels and no block in the middle (that big one, two masses are hanged on the same rope on only one wheel) does that make difference in Tension?

[jackwhite]

are 2015 frqs the only ones released for ap physics 1? btw thank you so much for every video. you are the best

[TheMrArtmaster]

AP Physics Exam in 3.5 hours. Great video! In the question, you said that although you derived the answer to the last part, we could have just explained it. On the exam, if we do derive it rather than explain with words, will we not get credit?

[dwp]

Ap test on Tuesday ;(
U deserve more views!