A gravitational field is a region of space where gravitational forces are exerted on masses. In other words, if a mass is situated in a gravitational field, it is going to experience a gravitational force.
The gravitational field strength g (at a point in a gravitational field) is defined as the gravitational force per unit mass (at that point). In theory, we can test the strength of the field at a particular position by placing a test mass m at that position. If the mass experiences a gravitational force Fg, then g can be calculated as
The direction of g is also defined by the direction of Fg.
Conversely, if a mass m is situated at a position where the gravitational field strength is g, it will experience a gravitational force of magnitude
in the direction of g.
Since a mass experiences a gravitational force of , it’s acceleration due to gravity is . So gravitational field strength and gravitational acceleration are the exact same thing. In fact, N kg-1 and m s-2 are equivalent units.
A 580 kg asteroid travelling in outer space experiences a gravitational force of 810 N.
a) Calculate the gravitational field strength at the asteroid position.
b) Calculate the gravitational force experienced by a 290 kg asteroid at the same location.
c) Calculate the acceleration of the asteroids.
c) 1.40 m s-2