# Doubt from kinematics

I get that involving maths using trajectory of projectile,but completely nonunderstanding

Mee ,too , please try 11,for questions 11 l done by mathematics by doing inclined plane as a tangent to trajectory of projectile,any other method???

**Viram_2019**#9

@Raghudevram_Singh

@pratyaksh_tyagi

You are throwing the ball from one edge A, it collides with the inner surface of the hemisphere, and comes back to A.

This is for question 12.

**Raghudevram_2019**#10

I just tried to find out point of intersection of parabolic path with semicircular curve but it transferred in to cubic. Whose one root is zero clearly but unable to do further

**Viram_2019**#11

@Raghudevram_Singh

I didnt get the answer but I think this is what happens. The ball collides at that spot where its velocity is in radial direction. Why? cuz then the velocity will be reflected as it is and the path will be retraced.

I think this is best method bro.

**Tanmay_1**#21

Pls see the solution...the question is true copy of the question in Krotov problems books on physics...most of the IIT coachings materials tken from russian books