Find the gravitational force between two 20 kg spheres that are separated by 4.0 m.

To find the gravitational force between two spheres, you can use the formula for the gravitational force:

F = G * (m1 * m2) / r^2

where F is the gravitational force, G is the gravitational constant (approximately 6.674 * 10^-11 N m^2 / kg^2), m1 and m2 are the masses of the two spheres, and r is the distance between the centers of the spheres.

In this case, the masses of the two spheres are both 20 kg, and the distance between them is 4.0 m. Plugging these values into the formula, we get:

F = (6.674 * 10^-11 N m^2 / kg^2) * (20 kg * 20 kg) / (4.0 m)^2

Simplifying the calculation:

F = (6.674 * 10^-11 N m^2 / kg^2) * (400 kg^2) / 16.0 m^2

F = (6.674 * 10^-11 N m^2 / kg^2) * (25 kg^2) / 1.0 m^2

Performing the multiplication:

F = (6.674 * 10^-11 N m^2 / kg^2) * (25) / 1.0

F = 1.6685 * 10^-9 N

So, the gravitational force between the two 20 kg spheres that are separated by 4.0 m is approximately 1.6685 * 10^-9 N.