Forces of gravity between two objects =
G · (mass₁) · (mass₂) / (distance between them)²
G = 6.67 x 10⁻¹¹ m³ / kg · s²
So the gravitational forces (one in each direction) are
Forces = (6.67 x 10⁻¹¹ m³/kg·s²) · (20,000 kg) · (12,500 kg) / (5 m)²
Forces = (6.67x10⁻¹¹ · 2x10⁴ · 1.25x10⁴)/(25) · (m³·kg·kg/m²·kg·s²)
Forces = (6.67 · 2 · 1.25 x 10⁻³ / 25) · (kg·m/s²)
Forces = (6.67 x 10⁻⁴) · (kg·m/s²)
Forces = 0.0001667 Newton (about 0.0024 ounce)
Note: The gravitational force acts between the centers of the objects, and that's where the "distance between them" is measured. For two masses of 20,000 kg and 12,500 kg, there's a chance that you might not even be able to get their centers with 5 meters of each other, even if they're made of concrete or steel. If not, then the gravitational forces between them would be less than 0.0024 ounce.)
