Question

Two balls are thrown horizontally from the top of a
building with speed u, and u, respectively in
opposite directions. The separation between two
balls when they are moving perpendicular to each
other, is (Acceleration due to gravity is g)
​

Answer 1

answer = 4m  

explanation : Let’s solve with different method.  

     here it is clear that balls are thrown horizontally so, the path of balls are parabolic. 

 it is example of horizontal projectile.  equation of path of horizontal projectile is y = gx²/2u²

where y denoted vertical distance e.g., height of ball from which it is thrown. x is horizontal distance, g is acceleration due to gravity and u is initial velocity of body.  

horizontal distance covered by first ball , x = \sqrt{\frac{2u^2y}{g}}=\sqrt{\frac{2(2)^280}{10}}=8mg2u2y=102(2)280=8m  

horizontal distance covered by 2nd ball, x’ = \sqrt{\frac{2u^2y}{g} } =\sqrt{\frac{2(3)^280}{10}}=12mg2u2y=102(3)280=12m 

 hence, The separation between the two balls when they hit the ground is (12m - 8m) = 4m