How strong is the force of gravity on earth?

1 Answer
Feb 21, 2016

The force of gravity is also known as weight, which changes for different objects. The gravitational field strength, or acceleration of gravity, is approximately the same everywhere on Earth's surface.


Gravity is a force of attraction that acts between any two masses. The bigger the masses, the stronger the force. That force also decreases with the square of the distance (ie doubling the distance means the gravity is 4 times less).

When you pick up an object, the weight you feel is the force of gravity between the Earth and that object. A heavier object is heavier because it has a larger mass, and therefore feels a greater force of gravity. So the question "How strong is the force of gravity" is not quite phrased correctly, since the force of gravity on an object depends on the mass of that object.

However, the gravitational field strength is fairly constant* across the surface of the Earth. This field strength determines how much force of gravity gravity (weight) any object will have. This field strength is 9.8 Newtons per kilogram of mass #(9.8N/(kg))#. What this means is a 1 kg mass will feel a downward force of 9.8 N. A 2 kg mass will feel 19.6N, a 500g mass will feel 4.9N, and so on. 9.8 N is approximately 2.203 lb.

*At the poles, the field strength is #9.83N/ (kg)#, and at the equator it is #9.78 N/(kg)#. A global average is #9.80665N/(kg)#, but that is a degree of precision that we cannot achieve, so #9.8 N/(kg)# is probably a better choice.