two vectors of equal magnitude have a resultant equal to either of them, then the angle between them will be equal to...? 


The resultant (R) of two forces (A and B) is mathematically represented as


 R2 = A2 + B2 + 2ABCosθ  

where θ is the angle between forces A and B. Now, as all three forces are equal, so

 let R = A = B = x


 x2 = x2 + x2 + 2x.xCosθ

or  x2 = 2x2 (1 + Cosθ) 

 1/2 = 1 +  Cosθ

thus ,  Cosθ =  -1/2

 or θ = 120o

The answer was calculated correctly by @prakharmilitary.


Hello @prakharmilitary ! good job, keep it going!

  • 55

Basically such a situation is not possible, but if we consider the motion in only a particular axis like X or Y. then the angle must be 90 degrees. then the component in the direction of anyone of them is equal to them.

  • -1

But in book D.C.PANDEY Mechanics..  it is given that this condition is possible...

  • -4

A^2=2A^2+2*A*A*cos x


-A^2/2A^2= cos x

-1/2=cos x  

then find cos x

  • 2

 and then cos equals 120 degree

  • 2
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