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If the resultannt of two forces of magni...

If the resultannt of two forces of magnitudes P and Q acting at a point at an angle of `60^(@)` is `sqrt(7)Q`, then P/Q is

A

1

B

`(3)/(2)`

C

`2`

D

4

Text Solution

Verified by Experts

The correct Answer is:
C
`R^(2)=P^(2)+Q^(2)+2PQcostheta`
`implies(sqrt(7)Q)^(2)=P^(2)+Q^(2)+2PQcos60^(@)`
`implies7Q^(2)=P^(2)+Q^(2)+PQ`
`impliesP^(2)+PQ-6Q^(2)=0`
`impliesP^(2)+3PQ-2PQ-6Q^(2)=0`
`impliesP(P+3Q)-2Q(P+3Q)=0`
`implies(P-2Q)(P+3Q)=0`
`impliesP-2Q=0` or `P+3Q=0`
From `P-2Q=0 implies(P)/(Q)=2`
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