Question #d7dc2

1 Answer
A08
Jan 23, 2017

We know with reference to the given figure that by Law of parallelogram of vectors

#|vecR|=sqrt(|vecP|^2+|vecQ|^2+2|vecP|cdot|vecQ|cdot cos theta)# .....(1)
and #alpha=tan^-1((|vecQ|sin theta)/(|vecP|+|vecQ|cos theta))# .....(2)

Inserting given values in equation (1) we get

#|vecR|=sqrt(|5|^2+|-3|^2+2|5|cdot|-3|cdot cos 60)#
#=>|vecR|=sqrt(23+9+2xx5xx3xx 0.5)#
#=>|vecR|=sqrt47#
#=>|vecR|=6.86#, rounded to two decimal places

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