1.

The resultant of two forces is 20 N when one of force is 20sqrt(3) N and angle between two forces is 30° then what is value of second force ?

Answer»

10N
20N
`20sqrt(3)N`
`10sqrt(3)N`

SOLUTION :`R^(2)=A^(2)+B^(2)+2ABostheta`
`(20)^(2)=(20sqrt(3))^(2) +B^(2)+2xx20sqrt(3)Bxxsqrt(3)/2`
`(20)^(2)=1200+B^(2)+20sqrt(9)B`
`-800=B^(2)+60B` or `B^(2)+60B+800=0`
SOLVING the quadratic equation B = 20 N


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