Acceleration due to gravity is about 9.8 m/s²
So after every second, the speed increase by 9.8 m/s
After 1 second, the object would fall at a speed of 9.8 m/s
After 2 seconds the object would fall at a speed of 19.6 m/s
So after 4 seconds, the object is going to be at a speed of:
9.8 x 4 = 39.2 m/s
-------------------------------------------------
Answer
39.2 m/s
