1.

Four particles, each of mass M and equidistant from each other, move along a circle of radius R under the action of their mutual gravitational attraction. The speed of each particle is:

Answer»

`(1)/(2) sqrt((GM)/(R )(1+2sqrt(2)))`
`sqrt((GM)/(R ))`
`sqrt(2 sqrt(2)(GM)/(R ))`
`sqrt((GM)/(R )(1+2sqrt(2)))`

SOLUTION :Net FORCE on any one particle

`=(GM^(2))/((2R)^(2))+(GM^(2))/((R sqrt(2))^(2))cos45^(@)+(GM^(2))/((R sqrt(2))^(2))cos45^(@)`
`=(GM^(2))/(R^(2))[(1)/(4 )+(1)/(sqrt(2))]`
This force will be equal to centripetal force so
`(Mu^(2))/(R )=(GM^(2))/(R^(2))[(1+2sqrt(2))/(4)]`
`u=sqrt((GM)/(4R)[1+2sqrt(2)])=(1)/(2)sqrt((GM)/(R )[2sqrt(2)+1])`
So correct choice is (a).


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