latika

2 tall buildings are 200m apart. with what speed a ball be thrown horizontally from a window of one building 2km above the ground so that it will enter a window 40m from the ground in the other?

2 masses m and 4m are placed at 12meter distance. where a mass of 10 kg can be placed between them so that the net gravitation force on it become zero.

5degree expected to drop4degree each hour for the next 3 hours what would be the temparture