chandrakantohekar2000

Suppose you are carrying a ball and running at constant speed, and wish to throw the ball and catch it back 
down. Should you (a) throw the ball at an angle of about 45º above the horizontal and maintain the same speed, 
(b) throw the ball straight up in the air and slow down to catch it, or (c) throw the ball straight up in the air and 
maintain the speed?

which concrete was used in burj khalfa ?