The acceleration due to gravity is `9.8ms^(-2)` and the mass has no effect on the velocity.
Assuming the inital velocity is 0, the velocity increases at a rate of `9.8ms^(-2)` .
So by 10 seconds the velocity is `10s` x `9.8ms^(-2)` = `98ms^(-1)`
And by 20 seconds, `196ms^(-1)`
The velocity increases linearly with time, the distance increases linearly with squared time. The formula for the distance is `t = 9.8/2 s^2`
The object takes `sqrt(2/9.8) s = 0.45s` to travel ```t=1` metre
and the speed at that point is `9.8ms^(-2)` x `0.45s` = `4.4ms^(-1)`
The average speed from 0 to 1 metre is `4.4/2 = 2.2ms^(-1)`
Check: `0.45s` x `2.2ms^(-1)` = 1 metre