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Three forces (2 hat(i) - 3hat(j) + 4hat(...

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:

A

10

B

20

C

-10

D

-20

Text Solution

Verified by Experts

The correct Answer is:
C
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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MODERN PUBLICATION-DESCRIPTION OF MOTION IN TWO AND THREE DIMENSION-Revision TEST
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