A male and female skater of equal mass are moving as shown in the figure above, with the female skater having a velocity of Ua at θ below the horizontal, and the male skater moving with half this speed at ϕ above the horizontal. When they collide, they cling to each other, and both of them move horizontally with velocity V.
For what range of angles θ is this possible?
Please help on mechanics physics question?
Announcements  Posted on  

TSR's new app is coming! Sign up here to try it first >>  17102016 

 Follow
 1
 06072016 16:44
Last edited by Jas1947; 06072016 at 16:48. 
 Follow
 2
 06072016 16:46
(Original post by Jas1947)
A male and female skater of equal mass are moving as shown in the figure above, with the female skater having a velocity of Ua at θ below the horizontal, and the male skater moving with half this speed at ϕ above the horizontal. When they collide, they cling to each other, and both of them move horizontally with velocity V.
For what range of angles θ is this possible? 
 Follow
 3
 06072016 16:48
(Original post by tangotangopapa2)
Which figure? 
 Follow
 4
 06072016 17:18
(Original post by Jas1947)
I've just edited the question, sorry about that, I was having trouble uploading it..
Assuming that collision took place with line joining centre of masses vertical, we can say following.
Note that component of velocity perpendicular to lines of centre is unchanged during collisions.
You could then solve the first equation further stating maximum value (sin phi) can take is 1 so maximum value sin theta can take is 1/2 and thus theta can be anywhere between 0 degrees and 30 degrees.
Hope this helps.Last edited by tangotangopapa2; 06072016 at 17:38. 
 Follow
 5
 06072016 17:57
(Original post by tangotangopapa2)
Assuming that collision took place with line joining centre of masses vertical, we can say following.
Note that component of velocity perpendicular to lines of centre is unchanged during collisions.
You could then solve the first equation further stating maximum value (sin phi) can take is 1 so maximum value sin theta can take is 1/2 and thus theta can be anywhere between 0 degrees and 30 degrees.
Hope this helps. 
 Follow
 6
 06072016 18:02
(Original post by Jas1947)
I've spent days trying to figure this out, now that you've shown me how to do it, it looks so simple...thank you so much! By the way...does this seem like an AS or A2 question to you? The site which I got it from says level 5 and i have no idea what that is. Thanks.
By the way, which site are you following?Last edited by tangotangopapa2; 06072016 at 18:03. 
 Follow
 7
 06072016 18:07
(Original post by tangotangopapa2)
You are welcome. Though the mathematics involved is simple, it could stun even A2 students. It looks like A2 question to me. 
 Follow
 8
 06072016 18:09
(Original post by tangotangopapa2)
You are welcome. Though the mathematics involved is simple, it could stun even A2 students. It looks like A2 question to me.
By the way, which site are you following?
https://isaacphysics.org/concepts/cp_cons_momentum 
 Follow
 9
 06072016 18:14
(Original post by Jas1947)
I was using Isaac Physics, heres a link:
https://isaacphysics.org/concepts/cp_cons_momentum
I think you should practice AS physics olympiad questions to really put you in test. Good luck!!!
http://www.physics.ox.ac.uk/olympiad/PastPapers.html 
 Follow
 10
 06072016 18:34
(Original post by tangotangopapa2)
Thanks.
I think you should practice AS physics olympiad questions to really put you in test. Good luck!!!
http://www.physics.ox.ac.uk/olympiad/PastPapers.html
"Reference Frames & Special Relativity". So I've used the mechanics links they've sent me on the Isaac physics website. But I don't know what reference frames or special relativity is. I've gone through the links and most of it is what I've covered in my AQA AS mechanics spec. Also, they mention a lecture about "Spin and angular momentum" and "Computing in physics,". But I've never done a computing class and I don't know where to even start with angular momentum. They've only asked us go over mechanics things but I don't know if they will expect me to know these other topics too. 
 Follow
 11
 06072016 18:54
(Original post by Jas1947)
Thank you, I'm actually preparing for a Physics university summer school. The main topic they've asked us to prepare for is
"Reference Frames & Special Relativity". So I've used the mechanics links they've sent me on the Isaac physics website. But I don't know what reference frames or special relativity is. I've gone through the links and most of it is what I've covered in my AQA AS mechanics spec. Also, they mention a lecture about "Spin and angular momentum" and "Computing in physics,". But I've never done a computing class and I don't know where to even start with angular momentum. They've only asked us go over mechanics things but I don't know if they will expect me to know these other topics too.
If I were to ask someone to go through Mechanics, then I would assume that they know Newton's Laws, can draw free body diagrams, know about conservative laws of nature, is comfortable with workenergy equations. But it seems that they want you to study a chapter called 'Rotation of Rigid Bodies'. Here is a resource I found: http://physics.gsu.edu/dhamala/Physi.../Chapter12.pdf
Good luck. 
 Follow
 12
 06072016 19:02
(Original post by tangotangopapa2)
Angular momentum is a huge topic, you need to go through circular motion > moment of inertia > dynamics of rotating body and will find angular momentum somewhere. You might want to go through the physics textbook you have and look for rotational motion. If you are OK with calculus i.e you have done Maths AS as well, then google the topics in the order mentioned above, you might find some good resources to learn from. Talking about Reference frames, it is simple concept so you should not have any problem, any YouTube video will do it for you but look for nonlecture ones. Then there comes the problem i.e. Special Relativity, which is beautiful in itself and counterintuitive too which talks about time dilation, length contraction and mass expansion. It is better to start with nonacademic material first. There are many good videos/ documentaries on it.
If I were to ask someone to go through Mechanics, then I would assume that they know Newton's Laws, can draw free body diagrams, know about conservative laws of nature, is comfortable with workenergy equations. But it seems that they want you to study a chapter called 'Rotation of Rigid Bodies'. Here is a resource I found: http://physics.gsu.edu/dhamala/Physi.../Chapter12.pdf
Good luck. 
 Follow
 13
 06072016 19:07
(Original post by Jas1947)
Wow the stuff on that link is completely brand new to me, I hope I don't look stupid when I get there...I can do all the basic things expected but I don't if I can understand all of this chapter. I don't even have a physics or mechanics book because it had to be returned to the college. Is this A2 level? Thank you 
 Follow
 14
 06072016 19:22
(Original post by tangotangopapa2)
Well, tbh not all of this is in A2 either. Not all exam boards cover angular momentum (edexcel does not cover it) and special relativity ( I don't know exam board that covers this topic, that's why I told you to go through non academic materials on this as mathematics is slightly difficult). 
 Follow
 15
 06072016 19:36
(Original post by Jas1947)
My timetable has only one hour on just 1 day for spin and angular momentum, so hopefully it might be just the basics? (No meaty questions for us to digest, I'm hoping).
One day for spin and angular momentum. It seems like they will throw summary of rotational mechanics to you. Make sure to ask for lecture notes on this.
Then I have about 90 mins on computing in physics (I still don't know what I should do for that).
Unless the programming language you will be using is told, it can't be prepared for. Mathematica and Matlab are good programming tools for Physics and also are easy to understand. Just tell them that you have no background knowledge in Programming.
And then I have Reference frames and special relativity for one hour each day for 3 days.
They should be able to deliver the stuff to you in this amount of time. It becomes much easier if you can digest concepts like time dilation, length contraction, mass expansion, and simultaneity principle (2 events can be simultaneous for one observer while not for other), and speed of light is constant and is the speed limit for any object. Ask for lecture notes on this one as well.
I also have a few practicals but there's no information on what I'll be doing. I've only found out about my timetable today. Before this I was just told to revise mechanics which I did in advance. I'm really worried about my ability to cope with the class after seeing these new specific topics.
Don't worry but try to grasp as much as you can. 
 Follow
 16
 06072016 19:44
(Original post by tangotangopapa2)
My timetable has only one hour on just 1 day for spin and angular momentum, so hopefully it might be just the basics? (No meaty questions for us to digest, I'm hoping).One day for spin and angular momentum. It seems like they will throw summary of rotational mechanics to you. Make sure to ask for lecture notes on this.Then I have about 90 mins on computing in physics (I still don't know what I should do for that).Unless the programming language you will be using is told, it can't be prepared for. Mathematica and Matlab are good programming tools for Physics and also are easy to understand. Just tell them that you have no background knowledge in Programming.And then I have Reference frames and special relativity for one hour each day for 3 days.They should be able to deliver the stuff to you in this amount of time. It becomes much easier if you can digest concepts like time dilation, length contraction, mass expansion, and simultaneity principle (2 events can be simultaneous for one observer while not for other), and speed of light is constant and is the speed limit for any object. Ask for lecture notes on this one as well.I also have a few practicals but there's no information on what I'll be doing. I've only found out about my timetable today. Before this I was just told to revise mechanics which I did in advance. I'm really worried about my ability to cope with the class after seeing these new specific topics.Don't worry but try to grasp as much as you can. 
 Follow
 17
 06072016 19:58
(Original post by Jas1947)
This looks so difficult, I'm only an AS student and I'm not the best at learning new concepts in a short space of time either. I'll try my best and hope that everything goes well. When you said, "It seems like they will throw summary of rotational mechanics to you. Make sure to ask for lecture notes on this." Where exactly do I get these notes from? I don't want to seem like I haven't tried to learn anything when I get there because I have been working really hard, just not in the area they might have wanted it in. Thank you
https://www.youtube.com/watch?v=3lp7...ew_PiJnQnuwOl
If you don't understand any of the videos then PM me. I will be happy to be able to help you. Just go through the videos in the order shown. (Warning : Very basic knowledge of Calculus is assumed). They should be more than happy if you learn these.
You usually get notes either from the lecturer or from respective department (i.e. Physics department).Last edited by tangotangopapa2; 06072016 at 20:01. 
 Follow
 18
 06072016 20:03
(Original post by tangotangopapa2)
The problem is due to the way Alevels is designed. For AS student that is slightly challenging to learn. I could find no better playlist on this.
https://www.youtube.com/watch?v=3lp7...ew_PiJnQnuwOl
If you don't understand any of the videos then PM me. I will be happy to be able to help you. Just go through the videos in the order shown. (Warning : Very basic knowledge of Calculus is assumed). They should be more than happy if you learn these.
You usually get notes either from the lecturer or from respective department (i.e. Physics department).
Write a reply…
Reply
Submit reply
Register
Thanks for posting! You just need to create an account in order to submit the post Already a member? Sign in
Oops, something wasn't right
please check the following:
Sign in
Not got an account? Sign up now
Updated: July 6, 2016
Share this discussion:
Tweet
TSR Support Team
We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.