Because gravity depends on mass and surface area. Is the object has more mass and surface area it will fall faster than the object with less. And thus, a sheet of paper falls slower than a coin under gravity through air.
1 5 1

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
The gravitational forces which pulls objects towards earth like magnet depends upon the  surface area of the object and the mass of the object .
Coin as more mass but less surface area and paper has less mass and more surface area hence there is more surface area and less mass paper falls slowly than the coin through air as much surface area prevents the paper from falling fastly than the coin
hope you understood 
with best regards sofia9
plz mark  it the best
2 5 2