9.807 m/s²
Acceleration defines the rate of change of velocity. It means, for acceleration of 9.81 (m/s)/(s) , the velocity will increase by 9.81 meter/sec.Suppose , a free falling body under gravity starts from zero speed. Then,After 1 sec, speed will be = 9.81 m/secAfter 2 seconds, speed will become 19.62 m/sec.So, more the time, higher will be the speed and with that speed it will strike the Earth.