Three force `F_(1) = (3hati + 2hatj - hatk)` `vecF_(2)` and that the particle may be in equilibrum , the value of 'a' is :

Options

A. -6
B. 6
C. 9
D. -9

Answer

A

Explanation

For equilirium
`" " vecF_(1) + vecF_(2) + vecF_(3)`
`(3hati + 2hatj- hatk) + (3hati + 4hatj - 5hatk) + a (hati+ hatj-hatk) =0`
`" "(6 + a)hati +(6+a) hatj -(6 + a) hatk=0`
`" " a = -6`