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Motion In A Plane

Question
CBSEENPH11026367

A stone projected with a velocity u at an angle 0 with the horizontal reaches maximum height H,. When it is projected with velocity u at an angle π2 - θ with the horizontal, it reaches maximum height H2. The relation between the horizontal range R of the projectile, H1 and H2 is 

  • R = 4 H1 H2

  • R = 4 ( H1 - H2 )

  • R = 4( H1 + H2 )

  • R = H12H22

Solution

A.

R = 4 H1 H2

We know that,

Maximum height of projectile equation is given by

      H= u2 sin2θ2 g

Where u = velocity of stone

         θ = angle 

 H = maximum height

       H1u2 sin2θ2 g

and   H2u2 sin2 90- θ2 g

since   H1H2u2 sin2θ2 g × u2 cos2θ2 g

                    = 44 × u2 sin2θ2 g × u2 cos2θ2g

             H1H2 u2 sin 2θ 216 g2

     [ since sin2θ = 2 sinθ cosθ ]

             H1H2R216

           R2 = 16H1 H2

           R = 4H1H2