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**Question on moment !**

## Homework Statement

Mb ( moment about b ) = 20k

B = (3,4)

F (force) = 5i-2j

## Homework Equations

Find the equation .

## The Attempt at a Solution

Mb =r*F

r= BA where A is a point on line of action of force

let A=(a,b)

r=A-B = (a,b) - (3,4) = (a-3,b-4)

Mb = (a-3,b-4) *(cross) (5i-2j) = (-2a-6)-(5b-20) k

( -2a-6-5b+20 )k = 20k

-2a-5b=6 ------> (1)

what to do else ?!

hope to help me

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