You accidentally drop a book down a stairwell. Assuming no air resistance,
how fast will the book be moving after 0.75 seconds?

if we drop it and not throw it then

after 0.75 how fast the book is falling is given by its velocity as

v= at

= 9.8 × 0.75

=7.35 m/s

moving ball hits still ball. mover stops, hit ball moves. momentum transfer.

the answer is b ) square root of 5