Q & A (Projectile Motion)

Q a projectile from a point O on the ground must hit a target P such that OP = 120 m The height of P from the ground is 60 m The minimum suitable velocity of projection is

(A ) 28 m/s (B ) 54 m/s (C ) 34 m/s ( D ) 42 m/s

IN THE SOLUTION PART THE FOLLOWING FORMULA IS USED

V min = √ g ( y + √ x ^2 + y ^2 ) AND THEY FOUND ANS ( D ) .

I DID NOT UNDERSTAND THIS FORMULA AND FROM WHERE THEY HAVE TAKEN .

Kindly help me in this regards.

Swapnil s khandekar
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The solution is attached in terms of two scanned images. Click on the images to enhance clarity.