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Motion In A Plane

Question
CBSEENPH11026337

Water level is maintained in a cylindrical vessel upto a fixed height H. The vessel is kept on a horizontal plane. At what height above the bottom should a hole be made in the vessel, so that the water stream coming out of the hole strikes the horizontal plane of the greatest distance from the vessel?

      

  • h = H2

  • h = 3H2

  • h = 2 H3

  • h = 34H

Solution

A.

h = H2

In general

Below equation is obtained from Kinematic equation

    v2 = u2 + 2ah

Instead of acceleration 'a' we used 'g'

The velocity with which water will came out

     v = 2 g ( H - h )

The time of flight of water ejected from the hole.

    t = 2hg = time of flight

∴ distance = velocity × time

⇒      x = v × t

         = 2 g H - h × 2hg

⇒       x = 4  Hh - h2 

For x to be maximum

     dxdh = 0

⇒   d h  Hh - h2 dH = 0

⇒   0 = H - 2h

⇒    h = H2