Originally Posted by **osalselaka** This question is according to the moment.
A. Think about the door. When I add a force of 10N which has perpendicular distance of 5m from the hinge, it has 10*5=50Nm moment. The force is acting by the place where I added 10N.
B. When I add a force of 10N which has perpendicular distance of 5m from the hinge, and another force of 15N is adding with no(0) perpendicular distance .Then the moment is (10*5)+(15*0).
In the A and B situations the moment is equal.
But I have the question that is,
the place where the total force is forming is change in A and B situations? (Practically when I do this experiment I felt same the two situations and therefore why the place of total force is forming is change in the two situations?) |

Do I understand your question to be:-

Configuration 'A' 10N acting on the door

Configuration 'B' (10N + 15 N) = 25N acting on the door

But

Why is the moment is the same in both configurations A and B?

Woody has partly answered this already.

We consider Force sums and Moment sums separately, they are independent.

In both A and B you have omitted another force, the hinge reaction.

This exactly equals the force sum (10N in A and 25N in B)

but

since it passes through the hinge it has zero moment about the hinge.

Does this help?