A cement block accidentally falls from rest from the ledge of a 51.6 -m-high building. When the block is 15.7 m above the ground, a man, 1.90 m tall, looks up and notices that the block is directly above him. How much time, at most, does the man have to get out of the way?

Answer 1

I think you mean a concrete block, not a cement block.

http://www.todayifoundout.com/index.php/2011/12/the-difference-between-cement-and-concrete/