Q43 of 43 Page 85

Two tall buildings face each other and are at a distance of 180 m from each other. With what velocity must a ball be thrown horizontally from a window 55m above the ground in one building so that the ball enters a window 10.9 m above the ground in the second building?

Let, initial velocity = u

Now, this is projectile motion. We can resolve the motion along X and Y axis.



u = velocity of projection


Since the initial velocity is along X-axis (horizontally)


Initial velocity along x-axis


Initial velocity along y-axis


= Acceleration along x axis


= Acceleration along y axis


Let, time taken to travel 180 m horizontally and (55–10.9) m vertically = t


So,





Motion along the Y axis,






Motion along X the axis






Hence, the ball must be thrown with the velocity


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