I. Mechanics(related Past papers' questions and discussion)
 

By the end of this month - May, I am planning to complete the very first portion of Physics, Mechanics, out of eight different portions. Underneath this post, and in this thread, the solutions of questions of the past fifteen years related to Mechanics will be posed. The basic aim of this thread will be to have a discussion regarding the different facets of the subject-matter and to save the past papers' solutions.

[B]All those who are going to opt Physics as an optional subject will be welcomed for sharing the stuff related to the portion, Mechanics, shared below with the bullet "I."[/B]

[I][COLOR="DarkOrange"]NOTE: Please do not comment below if you have any unrelated thing to share.[/COLOR][/I] (Sorry for an orange colour, as red is reserved for moderators maybe; but I hope you will not skip this important note)

[IMG]http://i.imgur.com/mtpnwm4l.jpg?1[/IMG]

Which is the correct numerical in paper 2000

Find the unit vector perpendicular to i+j and j+?
Or
Find the unit vector perpendicular to i+j and j+k

As per my knowledge second option is right and its typing error in first one. Reply must so i could try it:thinking

Physics-Vectors
 

Yes, it is "j+k."

Here is the solution:
[IMG]http://i.imgur.com/NDUYSnG.jpg[/IMG]

Redo this again, as I have just done it hurriedly. I hope it is correct; however, if you find any error, do mention it. :)

NOTE: I shall share another method as well, which involves matrices. That method seems more elegant to me than the aforementioned one.

Physics-Vectors(Same question as above)
 

Another method(Matrix method) just for confirmation.

[IMG]http://i.imgur.com/wG3ebK2.jpg[/IMG]

Error in uploading second image. Same method as solution 1 same answer. Finally i solved the vector problem without any help.:vic


[IMG]http://s23.postimg.org/avjp0yi7v/1432306718247.jpg[/IMG]

Calculate the angular momentum, about the Earth’s center of a 50 kg person on the equator of the rotating earth.

Check this. I am not sure



[IMG]http://s27.postimg.org/kn68ozmz7/20150522_210902.jpg[/IMG]

Angular momentum
 

Hey first of all, please use the vector notation where it is required. Otherwise, you will lose marks. Moreover, do not skip the pictorial representation of any question(where required).Those are the few things I noticed while checking your solution. Apart from that, you have correctly solved the whole problem. Also, do scrutinise my solution as well, for it will help us improve and revamp our concepts and solving methodology.

Here is my solution:
[IMG]http://i.imgur.com/JKKzdRB.jpg[/IMG]

Answers resemble but method is different. Your's is more authentic:bow

Check this also. If any other method, share.



[IMG]http://s9.postimg.org/j1s49rlkv/20150523_114733.jpg[/IMG]

Angular Momentum and Torque
 

That is how I solved:
[IMG]http://i.imgur.com/PVDiQEf.jpg[/IMG]
[IMG]http://i.imgur.com/CxyNb0p.jpg[/IMG]