If you drop an anvil from a height of 20 meters, how long before it hits the ground? why?

Question

what formula is used to solve this problem?

Answer 1

The basic equation is h=at^2/2 thus t=sqrt(2h/a).
Using 9.8 for a we get 2.02 s, just long enough for the roadrunner to reach the impact point when running at 20 m/s from 40.4 m away.