IIT JEE , AIEEE Forum - Physics , Mechanics - mechanics -- a total bouncer

bhupesh

First I must congratulate you in understanding physics in very physics way that should be the spirit keep on asking till you are satisfied .

Now about your question :

See the forces are vectors ( why ?? It makes mathematics easier, its hundred or two hundred years or so vectors are in use, other wise Mathematica Principia de naturalis phiosophie or mathematical principles of natural philosophy by Sir Issac Newton does not say about vectors ) to represent vectors we need a x-y axis. In Physics we name it frame of reference . The best part of it is you can chose your x-y axis as it makes you happy but intelligent choice would be If you would take the positive x in the direction in which the body is accelerating or has the possibility to accelerate the problem will be very easy as easy as adding two numbers . So chose the object in consideration as the origin draw a positive x-axis in the direction the body is acceleration or has the possibility to ( you said you know recognizing the forces ) draw the forces from the origin ( Its not mere mathematical origin but your object on which or by which forces are in action )

Now you can split the forces in to its components and you know the rest . ( if you are thinking of why we are splitting , adding three or more vectors through law of parallelogram is pathetic , so we split it and we add it if they are in same direction or we take the difference if they are in opposite direction )

Best of Luck and keep asking

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