1.

Three forces (2 hat(i) - 3hat(j) + 4hat(k)),(8hat(i) - 7hat(j) + 6hat(k)) and m(hat(i) - hat(j) + hat(k) keep a body in equilibirium. The value of m is:

Answer»

10
20
-10
-20

Solution :The vector sum of three forces should be zero
`:. (2hati - HATJ + 4hatk)+ (8hati - 7hatj + 6hatk) + m(hati -hatj + hatk)=0`
`(10 +m)hati -(10 + m)hatj + (10+m)hatk=0`
This eqn. is SATISFIED only if 10 + m = 0
`IMPLIES m = -10`


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