Question

An objective dropped from a height of 80 m. It will remain in air for time

Answer 1

ask the question clearly

Answer 2

As the case you have given is free fall.
Using s=ut +1/2 atsquare
Here u=O
A is - g
S=-s
Now we get s=1/2gt square
Time will be root over 2h/g
Substitute the value of h and you will get your answer.