Question

How do i calculate the magnitude of an unknown force,whats the formula for it

Answer 1

The magnitude of the force can be calculated, for example, using the second Newton's law:

$$F = ma$$

where $F$ is the net force on the body, $m$ is the mass of the body, $a$ is its acceleration. But the formula can be different in different cases, so it depends on the problem you are solving.