m

The first major Physics concept involved with this is Newton’s Second Law, which is summarized as F = ma. A consequence of this law is that if an object has a force exerted on it, the object will accelerate. Therefore, if an object is not accelerating then the sum of the forces acting on it is equal to zero. This applies to the problem, as the bar is not accelerating and therefore the sum of the forces acting on the bar will be zero.
The force acti...