The acceleration due to the gravity on the Earth's surface is 9.8 $\rm ms^{-2}$. This means that a body in free fall accelerates towards the center of the Earth at the rate of 9.8 $\rm ms^{-1}$ every second on the surface of the Earth. As a result, the body's velocity increases by 9.8 $\rm ms^{-1}$ every second in free fall.