Here's why:

* Gravity: It's the force of attraction between any two objects with mass. The Earth has a large mass, so it exerts a strong gravitational pull on objects near its surface.

* Acceleration: This means a change in velocity over time. Gravity causes objects to fall towards the Earth, constantly increasing their speed.

* 9.81 m/s²: This value is the average acceleration due to gravity at the Earth's surface. It means that for every second an object falls, its downward velocity increases by 9.81 meters per second.

Important Notes:

* The actual value of acceleration due to gravity can vary slightly depending on factors like altitude and latitude.

* The symbol "g" is often used to represent the acceleration due to gravity.

* The value of "g" is essential for many physics calculations, such as calculating the force of gravity on an object or the time it takes for an object to fall a certain distance.