Calculate Torque and directional force

[DrSammyD]

If I push forward on a box at a certain position, how do I calculate how much force will go into turning it, and how much force will go into moving it forward since it's not fixed to a position.

 

[Doc Al]

If I push forward on a box at a certain position, how do I calculate how much force will go into turning it, and how much force will go into moving it forward since it's not fixed to a position.

The entire force goes into accelerating the center of mass, per Newton's 2nd law, regardless of where on the box you exert that force. That same force will also exert a torque about the center of mass, which will tend to turn the box. The amount of torque you get depends on the angle the force is applied and its distance from the center of mass.

 

[DrSammyD]

The entire force goes into accelerating the center of mass, per Newton's 2nd law, regardless of where on the box you exert that force. That same force will also exert a torque about the center of mass, which will tend to turn the box. The amount of torque you get depends on the angle the force is applied and its distance from the center of mass.

Then I guess what I'm asking is, How much force do I have to push, where, and in what direction in order to have the box not move other than rotation.

 

[Doc Al]

Then I guess what I'm asking is, How much force do I have to push, where, and in what direction in order to have the box not move other than rotation.

There's no way to exert a single force and only get rotation. What you might want to do is exert a couple of forces--two equal forces in opposite directions. The net force will be zero, but the net torque will not be zero.