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-   -   Serious physics! (https://www.askmehelpdesk.com/showthread.php?t=247629)

  • Aug 11, 2008, 12:31 AM
    Rehaan_genius
    1 Attachment(s)
    Serious physics!
    Who can solve this?
    I think its not a difficult one, only concept based, but I get stuck with it!

    Attachment 11002

    Two inclined planes OA and OB having inclination 30degrees and 60degrees with the horizontal respectively intersect each other at O, as shown in the figure.
    A particle is projected from point p with velocity u=10 under root 3 m/s along a direction perpendicular to plane OA. If the particle strikes plane OB perpendicular at Q (take g=10 m/s^2) then,
    a) find time of flight from P to Q.(Ans:2sec)
    b) The velocity with which the particle strikes the plane OB.(Ans:10m/s)
    c) The height h of point P from the ground.(Ans:5m)
    d) the distance PQ.(Ans:20m)
  • Aug 11, 2008, 01:54 AM
    Rehaan_genius
    actually what I did for the first part is:

    I find the time when the initial velocity component becomes perpendicular to final velocity component which comes out to be u/gsin60=2 sec.
    but remaining parts..? I have no clue..!
  • Aug 11, 2008, 04:10 AM
    Rehaan_genius
    I just want to know which thing can I use to solve the remaining parts. I want to try myself!
  • Aug 13, 2008, 05:24 AM
    Rehaan_genius
    Hey administrator! Help me! No one has solved it yet!
  • Aug 13, 2008, 05:38 AM
    galactus
    Wouldn't part b just be
  • Aug 13, 2008, 05:54 AM
    Rehaan_genius
    Actually galactus! I don't get your hint!
  • Aug 14, 2008, 04:30 AM
    Rehaan_genius
    I got a hint which is;
    just rotate the axes along AO and OB means now AO is y-axis and OB is x-axis, but I am still not able to solve it!
  • Aug 15, 2008, 11:11 PM
    Rehaan_genius
    3 Attachment(s)
    Hi guys! I solved part a as follows;



    Attachment 11158
    Attachment 11159
    Attachment 11160
  • Aug 15, 2008, 11:51 PM
    Rehaan_genius
    1 Attachment(s)
    And part c as follows;

    Attachment 11161
  • Aug 16, 2008, 01:04 AM
    ISneezeFunny
    Part b

    As the hint says, rotate so that now AO becomes a tall building, and OB is the ground.

    Now, you've got a "if I kick a ball horizontally off a building" problem.

    You found out that AO is 10m

    And the entire thing took 2 seconds.

    ... which, by my math, should hit at 20 m/s...

    ... am I missing something here? I haven't checked your math for prev parts... so I'm not entirely sure, but if you're getting the right answers...
  • Aug 16, 2008, 02:32 AM
    Rehaan_genius
    3 Attachment(s)
    Part (b) is solved!

    Attachment 11164

    And part (d) is also solved!

    Attachment 11165
    Attachment 11166

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