An object falls with an acceleration of 9.8 m/s2. What is its speed after 2 s?

Acceleration is the rate at which velocity changes; here we are told the speed increases by 9.8m/s for each second of travel

assuming the object starts at rest, the object has a speed of 9.8m/s after one second, and a speed of 19.6m/s after two

mathematically, we write

v = at

where v is the velocity, a is the acceleration and t is the time of travel

so v = at = 9.8m/s/s x 2s = 19.6m/s