Set the two masses, then walk them apart. The gold arrows are the pull each mass feels — equal in size, opposite in direction, no matter how lopsided the masses are. The curve underneath is the real F = G·m1·m2 / r2: its guide lines each sit a quarter of the way down from the one above — 64%, then 16%, then 4% of full scale — so every time you double the separation the marker lands on the next line down.
Gravitational force F = G·m1·m2 / r2
2.670e-6 N
Each mass pulls on the other with this force. The two pulls are equal in size and opposite in direction.
Field strength of m1 at m2g = G·m1 / r2
2.670e-9 N/kg
Multiply by m2 to get the force back.
Force relative to r = 10 m
4.00×
Same masses, ten metres apart, would feel a quarter of this.
Separation
5.0 m
Mass m11,000 kg
Mass m21,000 kg
Mass m11 t
Mass m21 t
Separation r5.0 m
Gravitational constant G = 6.674e-11 N·m2/kg2.
Sliders are in tonnes; the formula uses kilograms, so 1 t feeds in as 1,000 kg.
Separation is measured centre to centre.
Arrow length is proportional to the force, on a scale pinned to these masses
at r = 10 m — that is the short tick on each arrow track. Changing a mass rescales
the whole picture rather than the arrow, which is why the plot's top-of-axis value moves
instead. Below about 2.5 m the arrow runs off the canvas and above about 18 m it bottoms
out at its minimum drawn length; the canvas says so when it happens, and the numbers
above stay exact either way.