[scientizscht (OP)]

Hello

If an object is hanging, how can I calculate the force to just start rotating it with minimal velocity?

Assuming no friction or any other obstacle from where it hangs.

Thanks!

[Bored chemist]

Any  non-zero force would start it rotating if there was no friction etc.

If you include the torque required to twist the suspension it gets more complicated.

Again this is one of your questions that is impossible to answer properly because you failed to specify it properly.

[Janus]

You have to supply a value for what you consider a "minimal velocity"? 
You have to have a time period over which you want to reach said velocity ( The shorter the time period, the greater the force needed to reach a given velocity.)
You need the moment of inertia for the object (which depends on the mass, shape of the object, and the orientation to the axis of rotation. (for example: a long  cylindrical rod has a different Moment of Inertia when rotated through its long axis than if rotated end over end)

The only situation where there would be some minimum force needed to start an object moving is when you first have to overcome some static friction.  For example, the static friction between a book and table can be greater than the sliding friction between same.  Thus it takes the application of more force to get the book to start sliding that it takes to keep the book sliding at a constant velocity once it starts to slide.

[evan_au]

The force also depends on whether you are using a lever.
- With a long lever, you need less force to get an object moving (to overcome static friction).
- If there is no friction, then there is no minimum force, but a lever can still help
- Of course, if there is no friction, and no gravity (eg in outer space), then it is very hard to start something rotating (or stop it from rotating), as some of the Space Shuttle missions experienced. Partly, because you have no fixed object against which to exert a force (the astronaut flies off into space, and/or starts rotating, too).

Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.

[Bored chemist]

Quote from: Archimedes
Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.

Thereby giving us the first documented failure of a research grant application.

[Janus]

The force also depends on whether you are using a lever.
- With a long lever, you need less force to get an object moving (to overcome static friction).
- If there is no friction, then there is no minimum force, but a lever can still help
- Of course, if there is no friction, and no gravity (eg in outer space), then it is very hard to start something rotating (or stop it from rotating), as some of the Space Shuttle missions experienced. Partly, because you have no fixed object against which to exert a force (the astronaut flies off into space, and/or starts rotating, too).

Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.

Or put another way, where you are applying the force to the object. In the cylindrical rod example, when you are rotating it end around end, it takes less force when applied near the end of the rod than it does closer to the midpoint.

[vhfpmr]

If an object is hanging

That phrase implies that there might be some gravity to overcome too, but as everyone else as said, if you don't ask a specific question you won't get a specific answer.