What does it mean to say that the gravity of the Earth is 9.8 m/s2?
The acceleration of gravity (also referred to as the gravitational field strength) at the surface of the earth has an average of
Gravity is a force, and according to Newton's Second Law, a force acting on an object will cause it to accelerate:
Acceleration is a rate of change of speed (or velocity, if working with vectors). Speed is measured in
An object dropped near Earth's surface will accelerate downwards at about
Since a large object will feel a large force of gravity and a small object will feel a small force of gravity, we can't really talk about the "force of gravity" being a constant. We can talk about the "gravitational field strength" in terms of the amount of gravitational force per kg of mass
It should be noted that the strength of gravity is not a constant - as you get farther from the centre of the Earth, gravity gets weaker. It is not even a constant at the surface, as it varies from ~9.83 at the poles to ~9.78 at the equator. This is why we use the average value of 9.8, or sometimes 9.81.
It means that any object is attracted by the earth towards its center with a Force
As per Law of Universal Gravitation the force of attraction between two bodies is directly proportional to the product of masses of the two bodies. it is also inversely proportional to the square of the distance between the two. That is the force of gravity follows inverse square law.
Combining the two we obtain the proportionality expression
It has the value
Mass of earth is
If one of the body is earth the equation becomes
See this has reduced to
Inserting the values
Simplifying we obtain
In other words if an object is dropped from a height