If I drop an object and it freefalls for about 10 sec how far will it travel?

Free-Fall means w/o air drag (or any other force except weight) so...

d = distance of Free-Fall = 1/2gt² {where t ≈ 10 s}

d = (0.5)(9.8)(10)² = 490 ≈ 500 m {since the time is "about 10 s" the answer is "about 500 m" }

490 meters.

D = D0 + V0*t + 0.5*a*t^2

4.9*10^2 = 490

That depends on the size of the object. And the pull of gravity. It varies depending on where you are in the world. For instance in the North Pole things fall veeery slowly on account of the gravity there being very mild.