a partical is projected on a horizontal plane at an angle 45 with horizontal from focous of a cacave mirror of curvature 'R' with speed v=squar root of (gR).velocity of particale when it just about to strike the horizontal plane.sir thanku so much for answering my doubt ful question

Dear student,

Use the formula:

1/u+1/v=1/f

Now differentiate and get the result...

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Sagar Singh

B.Tech, IIT Delhi

dear praveen , ur question is not clear ,can u please post the pic then it will be easier for me to solve...