Question

A phone falls out of your hand. If it hits the ground 1.8 s later how fast was it falling when it hit the ground?

Answer 1

The acceleration due to gravity is about 9.8 ㎨. This means that the speed increases by 9.8㎧ for every second it falls.
So after 1.8 seconds its speed will increase by 1.8×9.8=17.64㎧. The phone had no starting speed so it increased to about 17.6㎧.