When you stretch a spring 13 cm past its natural length, it exerts a force of 21 n. what is the spring constant of this spring?

Explanation:

From Hooke's law,

Substistuting the values, you can ignore the minus sign, since it is there to state that the force is always in the opposite direction of the deformation, and has no influence otherwise, and your constant is

the reason is because the moon has some form of gravity, and that gravity pulls the ocean tides.

grav forces affect all objects magnetic forces affect magnetic objects and electric currents