By how much does the speed of an object in free fall change each second?

With any object at any time the free fall acceleration is 10 m/s2

Explanation:

That is because when you throw a ball into the air it decreases by about 10 m/s each second, on the way down it increases its speed by about 10 m/s each second. So the the anwser is 10 m/s2.