# Doubt from kinematics

#23

Tanmay Sir pls help

#24

Ok let me try

#25

Regarding Q 12...the ball strike the hemisphere at angle theta
Then using law of reflection we get angle of reflection which is also theta
Because normal is the radius which is along range of prjectile
Directed to the centre of hemispher
Now the ball reach at the bottom most point of hemisphere
From that point in again gets reflected to reach at the point of
Initial projcetion.
SO I THINK (THETA+2THETA+THETA)=180DEGREE
SO THETA 45 DEGREE
SO IN MY VIEW tan(theta)=tan(45degree)=1
May be i am wrong...but i expressed my view.

#26

But answer given is tan ^-1 5/60, btw changing lengths given would.change answers naturally

#27

I can not visualise the physics in it...it will be better to find the source of this question and answer of it...in rebound case particle
Follow laws of reflection...in this problem what is ihe path ball will follow to reach its original point of throwing....

#28

Same here Sir , Samrat can u help ? Sneha can u also ?? ( leaving sometime besides studying for IMO Sneha ) ( pratyaksh sir can u also help ?

#29

#30

#31

#32
#33

![Screenshot_2019-08-01-07-21-22-1|690x200](uplo