What is the angle between two forces of equal magnitude, #F_a# and #F_b#, when the magnitude of their resultant is also equal to the magnitude of either of these forces?

1 Answer
P dilip_k
Jul 28, 2016

#theta=(2pi)/3#

Explanation:

Let the angle between #F_a and F_b# be #theta# and their resultant is #F_r# So

#F_r^2=F_a^2+F_b^2+2F_aF_bcostheta#
Now by the given condition
let #F_a=F_b=F_r=F#

So

#F^2=F^2+F^2+2F^2costheta#

#=>costheta=-1/2=cos(2pi/3)#

#:.theta=(2pi)/3#

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