# What does it mean to say that the gravity of the Earth is 9.8 m/s2?

##### 2 Answers

The acceleration of gravity (also referred to as the gravitational field strength) at the surface of the earth has an average of

#### Explanation:

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

#### Explanation:

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.

Mathematically

Also

Combining the two we obtain the proportionality expression

Follows that

Where

It has the value

Mass of earth is

If one of the body is earth the equation becomes

See this has reduced to

Were

Inserting the values

Simplifying we obtain

In other words if an object is dropped from a height